Playlist Folder Support for Music Providers

[MizterB]

Submitting per recommendation by @MarvinSchenkel on Discord

Some music providers allow playlists to be organized into playlist folders, which greatly improves organization. It would be useful to have the same concept supported in Music Assistant.

Currently, Music Assistant 'flattens' all of a provider's playlists into a single level both within the Playlist and Browse views. I would like to propose that at least the Browse view provide support for navigating a provider's playlist folder hierarchy if it has one.

In my current system, my Apple Music subscription contains over a thousand playlists, many with the same names. By organizing them into folders, it is easier to impose my own navigation system to quickly find what I am looking for. It has also eliminated the confusion of having many playlists with the same name at the same level of the hierarchy, and not knowing which playlist is which.

For Apple Music, it should be noted that Playlist Folders are not just an organizing construct, but are also considered a Playlists themselves. Therefore, it is possible to queue a Playlist Folder, and the resulting queue will contain all child Playlists below it in the folder hierarchy. I am unsure if this same concept exists for other providers, but I would also like to see this behavior extended into Music Assistant if the provider supports it.

There are some related feature requests / issues for specific providers:
#2894 - Allow Spotify Integration to view nested playlists.
#2472 - Concatenable/Nestable playlists

[soulstyle]

Really like to see this feature as well.
It would be great if this also included the possibility to create and organize your playlists in folders directly in MA :)

[Swimmer71]

This would be great. I just posted this comment here:

https://github.com/orgs/music-assistant/discussions/1256#discussioncomment-11302278

[cokefridge]

Absolutely. Folders are so underrated. Main reason for me to still use lyrion media server.

[arathilion]

I would also be very happy if the playlists could be displayed like in my app!

[dome2048]

Folders would be great and are really necessary for anyone with more than a handful of playlists.

[devedsmith]

I love this idea!