Base URL
https://spotify.dev.cl0sed.net
Link Spotify once, then let your iPhone shortcut call this Worker whenever you want to favorite the track that is currently playing.
Spotify app redirect URI: https://spotify.dev.cl0sed.net/auth/callback
Worker secrets: SPOTIFY_CLIENT_ID and SHORTCUT_SECRET. KV binding: STATE_STORE.
Shortcut request: POST https://spotify.dev.cl0sed.net/api/favorite-current-track?format=text with the header x-action-secret.
If saving fails, the Worker now includes the identified track in both the JSON response and plain-text error message when Spotify returned one.