fix(MusicManager): missing checks and reworked logic of who is the DJ

DJ is now the first user who makes the bot connect to a voice channel and doesn't change until the voice channel changes

src/main/java/me/bobert/netneutrality/tasks/music/AddAllTracksTask.java

@@ -41,13 +41,11 @@ public class AddAllTracksTask extends ButtonTask implements WithParent<LoadPlayl
     @Override
     public void execute(ButtonTaskContext context) {
         MusicManager manager = MusicManager.get(context.getGuild());
-        TrackScheduler scheduler = manager.getScheduler();
-
         Member member = context.getGuildUser();
 
         if (MusicUtils.connect(context)) {
             for (AudioTrack track : tracks) {
-                scheduler.getQueueManager().queue(track, member);
+                manager.getQueueManager().queue(track, member);
             }
 
             context.reply(MessageFunction.buildAddingPlaylistMessage(tracks, parentTask.getPlaylist().getName(), member, SourceFinder.AudioSourceType.Youtube));