Creates a playlist named "AllFavoriteSongs" or updates existing playlist with all favorite songs and all songs of favorite albums. Removes songs that have been unfavorited. Why? Because apparently shuffling through your entire library is not something the leading music streaming service should be able to do by default. But with this playlist you can! Can even download it for offline listening!
Note: Playlists are apparently limited to 10k tracks. At which point this script will likely spontaneously self-combust. Also, I have no idea how this interacts with podcasts or whatever else kind of content Spotify has.
ALSO: You need to set up an app here https://developer.spotify.com/dashboard/ because I'm not going to publish this as a real app with my own client id / secret