bluetooth multizone distribution

[markferry]

Have bluetooth players route audio via the server (and back through snapcast).

So that I can:

• play via Bluetooth to any or all zones
• add a Bluetooth A2DP receiver for zones where the player isn't nearby (e.g. outside or for amps with secondary zones)
• view metadata in Iris (and HA)

[markferry]

Pass bluealsa to trx?

Or plain tcp to snapserver.

Metadata?