botify 1 LTS

This long-term-support version of botify 1.6 marks the end of development for botify 1 while development shifts to botify 2 featuring a new web client and improved queue management.
As an LTS release this version will continue to receive bug fixes even after botify 2 is released.

update 1.6.LTS.21 28/02/2021

• Implemented rate limiting for command submissions
  • Commands can no longer be submitted more frequently than 4 times in 5 seconds with a timout of 1 second when acquiring the permission. If it cannot be acquired or if the execution queue is full the command is not executed and a 15 second timeout is raised.
• Updated dependencies
  • Updated several dependencies.

update 1.6.LTS.20 26/01/2021

• Handle audio event in separate thread
  • When using jda-nas all audio events are handled by the same thread that populates the native buffer, meaning when one playback finishes a track and loads the next track it blocks populating the native buffer for all playbacks. This is not an issue without jda-nas because in that case the events are handled by the audio connection thread of the specific guild.
• Check additional permissions when sending message
  • Check MESSAGE_EMBED_LINKS when sending embeds and MESSAGE_ATTACH_FILES when attaching files.
• YouTubeService#populateList: fix completing last item
  • The last item was never completed due to incorrect index comparison.

update 1.6.LTS.19 17/01/2021

• Change default launch option to running as jar
  • Use maven-shade-plugin to enable building shaded jar with all dependencies and adjust launch script to use jar as launch option and add HEAP_SIZE property to specify the -Xmx flag.
• Add property to adjust or disable native buffer duration
  • Add NATIVE_AUDIO_BUFFER property to enable adjusting the duration of the native buffer used by jda-nas. Also allows to disable jda-nas by setting the value to 0.
• Other improvements
  • Various minor improvements.

update 1.6.LTS.18 11/01/2021

• Use jda-nas to enable native audio streaming
  • jda-nas enables using native code to buffer and stream audio to reduce stuttering caused by garbage collection activity if supported by the current platform.

update 1.6.LTS.17 08/01/2021

• Improved queue widget
  • The queue widget now edits its message on reset rather than deleting and resending.
• Improved login command
  • The output of the login command was improved and the link is deleted after usage to signal that it cannot be used anymore.

update 1.6.LTS.16 31/10/2020

• Improved command parsing
  • Improve how arguments and the argument prefix is handled. If an argument prefix is followed by whitespace or is the last character of the command input it is treated as command input or as part of the argument value of the current inline argument definition.
  • Show better error message when encountering a malformed argument definition with an empty argument identifier.
  • Treat the character '=' as part of the argument value if already recording the value.
    • Previous encountering '=' would simply set isRecordingValue to true, which means it is essentially ignored if isRecordingValue is already true.
  • Throw an IllegalEscapeCharacterException if the CommandParser is in escaped mode when terminating, i.e. the last character was the escape character.
    • Previously the escape character would essentially do nothing in that case, which is more confusing to the user than the clear error message they now receive.
  • ArgumentPrefixProperty: validate that the argument prefix is not a reserved meta character as this could lead to unexpected behavior.
• other improvements and fixes

update 1.6.LTS.15 29/10/2020

• Improved Spotify to YouTube redirection
  • The algorithm to find the best YouTube video for a given Spotify track has been improved. Note that you might not notice an improvement right away as the old results are still stored and will get updated gradually over the coming month.
• Improved track loading error messages
  • Error messages shown when failing to load a track now reliably show the correct track when the queue has already skipped to the next track.
• Update YouTube API quota cost calculation
  • Update how the bot calculates YouTube API quota usage based on the changed quota costs.
• Various fixes, stability improvements and important dependency updates.

update 1.6.LTS.13 10/02/2020

• added last_used attribute to SpotifyRedirectIndex and adjust RefreshSpotifyRedirectIndicesTask to only regenerate indices that have been used within the last two weeks, else the index is deleted in order to reduce requests

update 1.6.LTS.11 08/01/2020

• added support for adding IPv6 blocks for IP rotation when executing certain requests

update 1.6.LTS.4 14/11/2019

• introduce automatic YouTube API quota management
  • calculate the approximate YouTube API quota cost for each request
  • when the quota usage reaches a certain percentage of the total
    daily quota limit specified in settings.properties, botify will
    switch to using lavaplayer to parse the html response instead of
    using the youtube API wherever possible
  • create CurrentYouTubeQuotaUsage entity with a single row that
    monitors the current quota usage
  • create cron job to reset the quota usage every day at midnight PST,
    which is when YouTube resets the quota
  • create startup task to reset the quota usage if it hasn't been
    updated or reset today, i.e. if the bot was offline when the cron job
    was supposed to run
• introduce JDA sharding
  • as the production system approaches 2500 guilds JDA requires to split
    the load across multiple shards with separate WebSocket connections
    or Discord will refuse to connect
  • use the ShardManager instead of a single JDA instance
  • the PropertiesLoadingService has been updated with extra convenience
    methods
• adjust some EmbedMessages to conform to the Discord design update

backend improvements

• added liquibase framework to run custom change sets on startup for schema changes that are not executed by hibernate hbm2ddl
• added entity validation through JPA annotations and created the EntityValidationInterceptor to validate entities during a transaction and send validation error messages to discord
• rework ISnowflakeMap to improve performance and thread safety
  • never iterate over the entry set but access the id map of the ISnowflakeEntrySet directly
• introduce VersionManager to streamline version management
• other minor fixes and improvements
  • YouTubeService#populateList: check if the PlaylistItems size does not exceed the amount of HollowYouTubeVideos generated for the playlist in case the playlist grew between checking its size and loading its videos to avoid and IndexOutOfBounds
  • CleanDbCommand: count guilds for which there is still a GuildContext cached as active; in case the guild returns before the GuildContext is cleared the GuildContext should not refer to a deleted GuildSpecification
  • ChartsCommand: skip Playables that are not available anymore
  • VoiceChannelListener#noOtherMembersLeft: ignore bots in the voice channel since leave and join events for bots are ignored

final release of botify 1.6

The last release of botify 1.6 focuses on improving and optimising existing features and the codebase. This update prioritised lowering the usage of the YouTube API quota, improving the Spotify redirect algorithm and fixing remaining issues.

• persist Spotify redirection results
  • create SpotifyRedirectIndex to persist the resulting YouTube videos in order to speed up the redirection process and save YouTube API quota
  • create RefreshSpotifyRedirectIndicesTask to refresh SpotifyRedirectIndices that have not been updated in 2 weeks
• Spotify redirect algorithm: improve the calculation of the Levenshtein distance
  • try several different combinations of track name plus artist and featuring artists to find the lowest possible Levenshtein distance for each proposed YouTube video title compared to the Spotify track
• rework WidgetActions to be executed via the CommandInterceptorChain
  • extract new Command interface from the AbstractCommand class
  • AbstractWidgetActions now implement this interface and are executed by the CommandInterceptorChain, like normal text-based commands
  • WidgetActions are now configured as XML contributions and instantiated per execution with a CommandContext instead of when setting up the widget
  • since AbstractWidgetActions are now executed via the CommandInterceptor chain there will now be a CommandHistory entry for executed widget actions, that means guilds that interacted with the bot via widgets will count as active guilds and will therefore not be cleaned up by the PlaybackCleanupTask (e.g. if a guild was playing a really long track and paused just before the task starts using the NowPlayingWidget, the playback would get cleaned up instantly)
• refactor ClientQuestion and Widget management
  • moved management of active Widgets away from the CommandManager to a new class
    • there is one instance of this new WidgetManager per GuildContext
  • moved management of open ClientQuestionEvents away from the GuildContext to a new class
    • there is one instance of this new ClientQuestionEventManager per GuildContext
  • enabled synchronisation for those new managers to avoid concurrent modification when iterating over the ClientQuestionEvents / Widgets
• other minor improvements and fixes

album covers, automatic Spotify track selection, automatic playback cleanup and other improvements

• when searching a Spotify track, botify now automatically picks the best result based on the likeness of the track names, track popularity and how popular each artist is in this guild
  • a selection of spotify tracks to choose from can now be fetched using the refactored "select" (formerly "limit") argument
  • the refactored "select" argument also does not necessarily require a value anymore but uses 10 (for YouTube) or 20 (for Spotify) as default value
• added album covers to the queue and "now playing..." widgets for Spotify tracks
• added a periodic task that resets playback settings and queues after an hour of inactivity to preserve resources and ensure long term stability
  • created framework to implement such tasks as cron jobs
• questions now get deleted when they are answered or otherwise destroyed either by timing out or being replaced by a different question and "still loading..." messages disappear once the reference command is finished
• other improvements and fixes
• backend improvements:
  • Launcher: make sure all guilds are setup within one session instead
    of opening and closing a new one for each by wrapping the loop
    inside one StaticSessionProvider#invokeWithSession call to make sure
    a thread session is setup and closed after all guilds are done
    • also setup guilds before running the startup tasks as some might
      require a guild context which meant guilds were set up twice,
      once implicitly when needed in the task and once explicitly when
      setting up the guilds later
  • VersionUpdateAlertTask: make sure all guilds are handled within one
    session instead of opening and closing one for each when sending an
    update alert to each guild
• added number of currently active guilds to the analytics command
• when loading playlists videos that were originally redirected Spotify tracks are now loaded and treated as Spotify tracks using the new BulkOperationService

additional commands and properties and other improvements

• create SynchroniseCommand to synchronise a botify playlist with an external playlist
  • in essence, this is an extension to the AddCommand that clears the playlist first
• create EmptyCommand to clear a botify playlist of all items
• add DefaultTextChannelProperty to customise the default channel per guild
  • MessageService#acceptForGuild now sends messages targeted towards a guild with no channel specified to the customised defaultTextChannel if possible
  • create AmbiguousCommandException to interrupt the command and ask a ClientQuestion from outside the AbstractCommand class during a command execution
• enable automatic removal of success and common error messages
  • create property to define the amount of seconds after which temporary messages are deleted
    • a timeout of 0 means there is not timeout
  • success and common error messages are now temporary messages that
    are removed after the time specified by the tempMessageTimeout
• several fixes and improvements

improve concurrent command handling and other improvements

• create abort command to interrupt current commands and cancel
  queued commands
• commands can now be set to ignore the queue and run even if the
  queue is full
  • applied to admin commands and the new abort command
• widgets execution threads now do not get added to the queue but
  always run
• add size limit to AudioQueue
• adjust add command to only use the invoke method when needed and not
  put the entire command into an invoke call so that several add
  commands entered by the same guild can load tracks at the same time
  but not alter the playlist at the same time

command parser, expand ClientQuestEvents, argument prefix, JDA 4

major new features

• create CommandParser that enables escaping meta characters through
  an escape character "\" or using single or doubles quotes and makes
  using arguments smarter and less strict
  • inline arguments are now treated as regular arguments and can be
    used as such, when used as an inline character the value of the
    argument will be the input following the argument up to the next
    argument. The order in which inline arguments are used no longer
    matters. Meaning insert a $to b $at c could also be written
    insert a $at c $to b or even insert $to=b $at=c a.
  • argument values may now contain whitespace by putting the value in
    quotes like command $arg="some value"
  • enables using escape characters and quotes to escape meta characters
    e.g. play $spotify \$trackname or play $spotify "$trackname"
• enable selecting several options comma separated when asked a question
• add an option to select all options when asked a question by certain
  commands
• add property to customise argument prefix
  • create CommandParseListener for the new CommandParser to update
    argument prefixes in existing Presets when changed
• add monthly charts to charts command
• help command examples now use the custom prefixes

other technical improvements

• upgrade to JDA 4
• refactor PlayableFactory to create Playables for Spotify albums and
  playlists and YouTube playlists when they appear in the provided list
  of objects for any method that returns a List of Playables
  • this was done to simplify #withUserResponse implementations if the
    user uses the new feature to select several options
• create AudioManager#startPlayback and #startOrResumePlayback
  instead of relying on Playable#matches to automatically determine
  whether the current track is the track that should be played or if the
  skip or rewind commands / actions were used because in rare cases the
  Spotify id might be null in which case the method is unreliable
• add Playable#getDisplayNow and #getDurationNow to use in queue view
  handler instead of using a timeout to further reduce loading time
• make Playable methods throw an UnavailableResourceException instead of
  InterruptedException when trying to access a cancelled item because
  an InterruptedException does not quite make sense
• make the the permission all attribute ignore admin commands
• optimise ThreadExecutionQueue to synchronise #add and #runNext to make
  sure a thread can't be added at the same time as another one finishes
  and tries starting the next one, creating a window where potentially
  one thread to many could run at the same time
• move GuildManager#getNameForGuild and #getPrefixToGuild to the
  GuildContext so the GuildContext
• create AdditionalInformationException for exception classes that
  show addition hints, separating the long hint from the error message
• create session in CommandListener to load bot name and prefix with
  instead of creating a session in both methods

improved Spotify redirect algorithm and added more javadoc

• the redirection of Spotify tracks to YouTube has been made smarter by generating a match score based on whether or not the artist appears in the channel title, the similarity of the track / video titles and the view count
• a lot of new javadoc has been written for previously undocumented classes
• added handling for rare cases when loading a Spotify playlist's tracks, getting the Track for a PlaylistTrack might result in null

Final stability update for botify 1.6.1

Last updates:

• update lavaplayer dependency to fix loading some YouTube videos
• print java version on startup

enable silent updates and improve some old code

• enable silent updates, meaning no update notification will be sent if there are no changes that might interest the user
  • the reboot, quit and cleandb commands can now also be used without informing the active guilds
• fix export command failing when an early flush is caused by the query for artists when creating a Song by persisting the Playlist first to avoid a TransientObjectException
• improve upload command and Playlist#asTrackList
  • Playlist#asTrackList was an old inefficient method that loaded
    each track separately, which could cause a TooManyRequestsException;
    now it loads the maximum of 50 tracks per request
  • remove the Thread#sleep
    • the TooManyRequestsException that would get thrown there was just
      a product of the bad Playlist#asTrackList method
• fix Playable#matches throwing a NullPointerException when the parameter is null by returning false

additions and improvements to admin tools and fix remaining issues

• create CleanDbCommand and GarbageCollectCommand
  • the CleanDbCommand cleans all data associated to guilds the bot is no longer part of
  • the GarbageCollectCommand start a manual garbage collection to free up memory when convenient
• fixed appending the UpdateCommand output as file when too long
• fixed AudioManager#playTrack behaviour when unpausing the playback after the bot left the channel
• improve performance of MessageService#sendToActiveGuilds
  • instead of looping over each guild and firing up to two queries per guild, only create two queries in total to find all guilds that recently played a track or entered a command
• make sure that operations that use Botify#shutdownListeners re-register the listeners when an exception happens
• show properties with null values as "Not Set"

charts command, additional properties and several bug fixes and improvements

• added charts command
• added properties to select the default source (Spotify, YouTube, local) when searching a track or list
• added property to toggle the auto pause feature
• fixed behaviour when skipping a paused track that just resumed the track without skipping
• made adding playlist items in the correct order more reliable when adding tracks from different sources at the same time
• fixed issue when rolling back invalid property values where the wrong value would stay cached and break the property
  • added proper ehcaching and made sure GuildSpecification entities are operated upon in the same session that created them
• added caching for AudioTracks that resulted when loading a Playable using soft references
• fixed error when playing cached AudioTracks by always cloning them beforehand
• fixed error handling in MessageService causing additional errors when trying so send the error as an EmbeddedMessage with missing permissions to do so

rework of the code base, guild properties, admin commands, spotify URIs

New features

• add a whole new category of commands: admin commands

  • these commands provide core functionality like restarting, updating
    and quitting the bot with an added bonus that if the bot is shut
    down that way it will wait for pending commands and rest actions to
    complete

• add adjustable guild properties for deeper customisation

  • properties are guild specific settings persisted as columns on the
    GuildSpecification and have a default value
  • they can currently be used to change the colour scheme and toggle
    "Now playing..." messages
  • the bot name and prefix were also implemented as properties

• add support for Spotify URIs

  • added a class that recognises and parses Spotify URIs and creates
    playables based on the URI's type (currently track, playlist and
    album)

Large user orientated improvements and changes

• rework Permission command and add more arguments to manage several
  commands at once
• create SecurityManager and apply command permissions to widget actions
• redesign the queue widget using emojis to display the enabled options
  instead of creating a field for each option
• add enabled options to the footer of the "Now playing..." messages
• fix widgets throwing an exception when attempting to skip or rewind
  when the queue is empty
  • handle this in the widgets and improve the exception thrown by the
    AudioQueue
• redesign help command to be more compact
• rework the behavior of the "own" keyword
  • make it work with albums
  • still use a regular spotify query and then filter the results using
    the SpotifyApi#checkUsersSavedTracks method instead of loading
    all of the users tracks and then filtering the results
    • this means the spotify query syntax can now be used with this
      argument
• remove PendingQuestionRemovalInterceptor
  • ClientQuestionEvents are no longer removed when entering a different
    command

Large changes to the code base

• create Botify as a statically available class that provides access
  to all of Botify's managers and add core functionality like shutting
  down or restarting the bot
• create Cache class to aid reflective instantiation of classes and
  provide cached instances for constructor parameters
  • replaces the ParameterContainer
• migrate GuildSpecifications to the db
  • this servers as a preparation for moving the bot to sharding some
    day
• add Current class to CommandContext to enable static access to the
  current thread's CommandContext
• create StaticSessionProvider to provide hibernate sessions based
  on whether a CommandContext is set up

Other changes and improvements

• rework Widgets and create AbstractWidgetAction class that also manages
  permissions required to use a specific widget action
• create QueueIterator to better manage iterating the queue
  • use this class as the AudioEventAdapter for the respective
    playback instead of using AudioManager for everything
  • this class in instantiated for each AudioPlayback each time a
    playback is started and replaced when a different playback is
    started. This improves handling when the queue is iterating in a
    loop over unplayable tracks
  • limit the amount of invalid tracks skipped automatically to avoid
    a frozen queue, spamming the chat or even a stack overflow
• add id to playable and use this id when creating a playback history
  to prepare for the charts command
• rework CommandInterceptors and create CommandInterceptorChain
• use Sets instead of Lists for relations on hibernate entities
• LoginCommand: check if the user actually received the message and
  make the corresponding method in the MessageService return the
  message
• cancel login refresh tasks when a login is destroyed by a logout
• add a timout function when waiting for values of a playable that is
  currently being loaded
  • implemented for Playable#getDisplay and Playable#getDurationMs
  • this speeds up loading the queue view page when the queue is
    currently being loaded, displaying playables that aren't done yet
    as "Loading..."
• create PlayableFactory and move away the createPlayable methods from
  the AudioManager
• create GuildTrackLoadingExecutor and move loading tracks away from
  the AudioPlayback class
• delete PlayableImpl and split it up into the TrackWrapper for Spotify
  track previews and make the YouTubeVideo interface extend Playable
• create SpotifyService and phase out SearchEngine, using it only for
  local playlists
• remove DiscordListener and split it into several different listeners
• move adding the annotated classes to the hibernate configuration file
  and use a more recent method to build the SessionFactory that supports
  this
• create AbstractQueueLoadingCommand as a super class for the play
  and queue commands to merge their similar code
• remove channel parameter from AbstractCommand#sendMessage and the
  user parameter form AbstractCommand#runWithLogin as they were always
  getContext.getChannel() or getContext.getUser()
• split up AlertEventListener into several interceptors, one for each
  entity, create a super class for this kind of interceptor and create
  a new interceptor that alerts changes to the access configuration
• create and export command: check if the playlist count and size
  properties are empty
• MessageService: make common timeout errors when sending messages take
  up less space in the logs
• replace old java.util.Date with java.time.LocalDateTime
• HttpHandlers: add some utility methods to handle parameters and errors
• update guava and lava player

move and insert commands, ThreadExecutionQueue, Playlist indices etc.

• create move and insert commands to move items within playlists.
  • to enable this playlist items are no longer sorted by create
    timestamp across the tables but by the new item_index column
  • a startup task has been created to migrate the existing playlists
  • a listener verifies and sets the item_index values for newly
    created or altered playlists
• the CommandManager now always searches for commands and presets
  • previously it only searched for presets if no command was found,
    meaning if you had a preset that starts with a command name
    (e.g. "playlist") it would not find the preset
    • if it finds both it takes the longest match, when both are
      exactly the same it favours the command over the preset
• create ThreadExecutionQueue and CommandExecutionThread to manage
  how many commands can run concurrently per queue
  • All commands are now run as a CommandExecutionThread, meaning the
    CommandContext is easily accessible from everywhere during the
    command runtime. This fixes an issue where the wrong or no message
    channel was passed to the exception handler for track loading
    threads.
• the Youtube redirect for Spotify tracks no longer just takes the best
  match according to YouTube but analyses the three best matches,
  checking whether the channel name contains the artist and comparing
  levenshtein distances
• "Could not load track messages" now delete each other like the
  "No playing" messages to prevent spam and it ignores if repeat all
  is enabled to prevent infinite spam
• create NoSpotifyResultsFoundException that adds a hint about how to
  use Spotify queries to the message when no spotify tracks were found
• raised the bot name limit for the rename command from 10 to 20
• AbstractWidget now saves the guildId as a field since message#getGuild
  could cause garbage collection issues
  • this fixes a problem where older widgets could not be deleted
• AbstractWidget no longer adds a delay when adding reactions, deletes
  old widget instead
  • the delay was added to avoid problems with the rate limiter when
    adding reactions to the new widget while removing them from the old
    one; now the old widget just gets deleted
• the CommandVerificationInterceptor no longer allows the command input
  to be longer than 1000 characters
• verify playlist names and correct them if they have more than one
  space consecutively
  • Discord would omit the unnecessary spaces when displaying the name,
    causing confusion
• create PersistTask class to create tasks that are used in several
  locations
  • e.g. HibernatePlaylistMigrator and UpdatePlaylistItemIndicesTask
• adjust the add command to be extendable by the insert class, so only
  the few things that are actually different about the command had to
  be overwritten
• add method to AbstractCommand to only split a part of the command body
  by an argument
• CommandContext now has a UUID that is added to error messages to help
  finding them in the log
• add a new method for each event to the ChainableInterceptor that gets
  called by the regular method which handles all thrown exceptions and
  calls the next interceptor in the chain without having to do so
  explicitly in the Interceptor implementation
• add a shared invoker for all guilds in case the mode is not
  partitioned
  • since, when mode == SHARED, all guilds access the same playlists
    they should all be synchronised
• PlaylistItems are no longer added to the respective collection on the
  playlist in the constructor but manually when calling the new add()
  method
  • this allows the insert command to check if the playlist is empty
    when the items have already been created but not yet added
• log all exceptions thrown in httpHandlers

fix presets containing a single quote

make preset search case insensitive & bug fixes

• presets are now recognised disregarding their capitalization when
  entered
• fix commands not being parsed correctly due to case sensitivity
• fix bug in search command when searching for Spotify
  albums / playlists with less than 5 tracks
• correct some typos
• no longer alert name change on startup

command presets, volume command, customisable command prefix etc.

• add command preset feature
  • Command presets can be used as shortcuts for lengthy commands or
    creating an alias for a command. Presets han hold one variable
    marked by "%s" that may be assigned a value when using
    the preset.
• add volume command to change the music volume
• add customisable command prefixes to start commands separate from
  the bot name
• update notifications now show new features
• send a getting started message when a new guild joins
• add examples section to help command
• fix an issue where playlist tracks do not get played in the correct
  order
• fix an issue where the search command fails when displaying a short
  local playlist
• the "Now playing..." widget now shows the next track considering the
  repeat settings
• the queue command now shows the playback settings even when the queue
  is empty
• automatically unpause playback when playing a different track
• make CommandExecutor a CommandInterceptor and have one separate
  synchronised Invoker per guild
• refactor AudioQueue
• create Table2 class to help create a table in an EmbedMessage

1.5 hotifx and several technical improvements

• the permission command no longer requires input, so that flag had to
  be changed
• handle unavailable YouTube videos when attempting to load their
  duration
  • contentDetails is null for unavailable videos, just return 0 instead
• synchronise the CommandExecutor#invoke method on the guild that calls
  it
  • making sure the same guild can not run this method concurrently.
    This is to counteract the spamming of a command that uses this
    method, e.g. spamming the add command concurrently could evade
    the playlist size limit.
• auto reformat all code in the project
• MessageService: do not log the stack trace for warnings when a
  message could not be sent because of permissions
  • this just spams the logs adding no value

introduce widgets, add new "reverse" and "forward" commands,
support Spotify query syntax and other major changes

• introduce widgets. A widget is an interactive message that can be
  interacted with by adding reactions. Different reactions trigger
  different actions that are represented by the reaction's emote.
  They can be used to create a simple player UI.
• support the Spotify query syntax to filter results when searching
  for Spotify tracks.
  • The "artist:" and "album:" filters can be used as such:
    $botify play from the inside artist:linkin park album:meteora
• "Now playing..." messages have been redesigned and are now widgets
  that can pause / unpause the playback and skip / rewind tracks
• The queue display is now also a widget with controls to:
  • enable / disable shuffle, repeat one and repeat all
  • play / pause the queue
  • skip / rewind tracks
• add "forward" and "reverse" commands to change the position of
  the current track
  • Skip or rewind the given amount of seconds or minutes in the current
    track.
    E.g. $botify forward 110
    $botify reverse $minutes 2
• delete old "Now playing..." messages when a new one is sent so the
  channel does not get spammed.
• check if input is a URL before checking arguments for several commands
  • the arguments $spotify, $list and $youtube are intended to tell the
    bot where to search for the entered search query, yet some users
    use, for example, the $youtube argument when entering a YouTube
    URL, in which case it would search for a video with the URL as name,
    finding nothing. Now the bot first checks whether the input is a
    URL, ignoring arguments if that's the case.
• update permission command with the option to show a list off all
  commands and who can access them.
• update and improve some command descriptions explaining better how to
  use them.
• add support for the discordbots.gg API to update the bots statistics.
• recognise youtu.be URLs as YouTube URLs and treat them accordingly.
• handle throwables returned by lava player when loading tracks and
  print them to the channel.
• style success and error messages.
• some command outputs (e.g. queue, local list search and client question)
  are now lists rather than tables with several embedded fields, because
  the content of one row was often too long, meaning all columns could
  not fit next to each other, resulting in the columns being aligned
  vertically.
• All InvalidCommandExceptions now add a hint to use the help command.
• updated SearchEngine
  • get rid of the MAX_REQUESTS property and load everything until
    there is no page left.
• minor refactor for AlertService (renamed to MessageService).
  • all methods now return a CompletableFuture for the Message they
    are sending, since the completed Message objects are used by the
    widgets.
• add C3P0 connection pool configuration instead of using hibernate's,
  which is marked unsuitable for productive systems.
• CommandExecutor#invoke is no longer synchronised, since it is no
  longer required.
  • when pk's were not generated with strategy GenerationType.IDENTITY
    there could be an issue when creating entities concurrently, but
    since that is no longer the case running the invoke method
    synchronised is pointless.
• update readme.

add clear command and various bug fixes and improvements

• add clear command that clears the current queue of all tracks
  (except the currently playing track)
• update dependencies
• fix YouTubeService#getAllVideos method not loading video IDs
• help command: ensure correct order of commands by using a
  LinkedHashMultimap
• improve some command descriptions to better explain what they do
• AlertService: add stack trace to one warning

handle insufficient permissions when sending message to guild