Switch join unjoin services called for linkplay media players

[MahrWe]

Update the services join and unjoin called for linkplay based devices.

The group_members attribute for linkplay devices lists UUIDs instead of entity ids which is currently not handled correctly by mini-media-player.

Adresses: Linkplay integration moving into core #866

[benbender]

As I would love to use this to manage grouping of my linkplay devices, I would love this to be merged. Any reason why this is still a draft? What is missing?

[MahrWe]

This Pull request breaks compatibiltiy with the outgoing custom-integration. At the same time mini-media-player will still not work with the new core-integration.

I see different paths forward, both are over my programing capability:

1. distinguish custom- and core-integration (both named linkplay) in the code (to not break comp.)
2. update the core-integration to use entity-ids in the "group_members" attribute.

@silamon might understand enough about the multiroom functionality of the core-integration, to know if 2) is possible.

Also see the issue I created on this topic: home-assistant/core#133042

[silamon]

The group_members returning the wrong ids is a bug in core integration, it's on the list to get fixed eventually. I need to rewrite the logic to keep a mapping as well, that's why it's taking a long time to get it fixed.

[benbender]

thx for the clarification and the work you are putting into making these features work seamlessly! very much appreciated! <3