Has anyone created a bubble app that allows a user to login with Spotify and then pre-saves the album to their account?
For Spotify you will need to use OAuth2 to allow a user to login with Spotify.
This link should point you in the right direction
After that you can use the Spotify Web API allow interactions between Spotify and your Bubble app.
The Spotify Web API is Rest based so you can use the Bubble API Connector to connect with it easily.
The link below should help you in understanding the Spotify Web API
I have used MusConv tool to transfer all my Spotify playlists to Apple Music without any hassle.
It also has interesting features like:
Transfering unlimited tracks, transfering unlimited playlists, supports over 20 playlist file formats.
You can use MusConv to transfer songs between apple music and spotify. I’ve been using it and I think it has been the easier way to transfer playlist from one to another.