feat: Make users follow/unfollow playlists when they join/leave lobby

[darren2hang]

• Add followPlaylist function which uses the Spotify PUT endpoint to make a user follow a playlist
• Add unfollowPlaylist function which uses the Spotify DELETE endpoint to make a user follow a playlist
• Have the user addLobby and removeLobby functions call the followPlaylist and unfollowPlaylist function
• When a user creates a lobby, their spotify account will also follow the spotify playlist
• When a user joins or leaves a lobby, their spotify account will also follow/unfollow the spotify playlist, respectively
• When a manager of a lobby deletes a lobby, the manager and all the users in the lobby will also unfollow the spotify playlist

[mergify[bot]]

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