Implement playlist folders

[binyamin]

On the official Spotify clients, you can nest playlists under a given title. In other words, you can create folders filled with playlists.

I have a lot of playlists, and folders ensure my music is organized, and keep my sanity intact. Spotify's default styling should work fine with this interface.

:point_down: example :point_down:

[Folder title]

Playlist 1
Playlist 2
Playlist 3

[ShawkMusic]

Yeah I would like to have this too

Makes organizing much easier

[jacksongoode]

It looks like folders are unsupported by the API. I imagine it might be possible to create folders local to Psst?

Edit: There is a 3rd party solution if one has a Spotify cache present - might be a nice alternative. What do you think @jpochyla?

[jacksongoode]

Just thinking that this could be feasibly rewritten in Rust and then add an optional import option in the account/preferences modal that would check the user's playlists against the cached folder structure on load and fill them in accordingly. Those playlists that don't exist in folders would appear outside.

It might also be helpful to have a remove button as well to drop the structure if desired. The parsed json could either be regenerated on load to look for changes or remain static until the user click's import again to update a changed folder structure.