src/livekit/auth now fronts two flows. For a transport with a LiveKit SFU
`url`, tokens come from our own homeserver's MSC4195 get_token endpoint
and delayed leaves are delegated through delegate_delayed_leave, both via
the js-sdk's unstable client methods. Transports with only a
livekit_service_url keep using the OpenID flow against the JWT service.
A transport advertising both shapes lets a subscriber fall back to the
OpenID flow when the homeserver answers get_token with a 404 (Synapse
reports M_UNRECOGNIZED for unknown routes rather than M_NOT_FOUND), so a
client can still join calls hosted on servers that have not deployed
MSC4195 yet. Publishers never fall back: a homeserver that advertises a
`url` but does not implement the endpoints is misconfigured and the
admin should hear about it, so they get NoMatrix2AuthorizationService.
Delegation uses the same flow as the token so that the participant
identity the service computes matches.
The local member only probes a transport's delegate_delayed_leave
endpoint when it has a service URL. The developer settings tab validates
a custom service URL through the same facade.
The OpenID flow moves to src/livekit/auth/openID.ts with the SFU config
types in a sibling file, takes an options object, and replaces the
MatrixRTC mode with the role we take on the transport plus the session's
slot ID instead of a hard-coded m.call#ROOM.
This changes behaviour: publishers on a livekit_service_url transport
always use the legacy /sfu/get endpoint, so that subscribers can predict
their user:device participant identity, and subscribers always use the
default /get_token endpoint. The MatrixRTC mode no longer influences which
endpoint is used.
Johannes Marbach