Exposing LiveKit status in site settings serializer

[Falco]

@nicolsdennis

after reviewing for past 5hrs I tagged the members from the core commit/merge of voice.

If you think 5h is too much to wait, you may be new to the concept of async comms in forums. Welcome!

@nicolsdennis

RoomSerializer#expected_transport covers the per-room case nicely, but that requires fetching rooms first, and it comes back empty when voice_public_access is off, even on a site where LiveKit is fully configured.

I will investigate this and come up with something we can use.