[SDK] Let developers override the whole transport

The developer setting that overrode the LiveKit service URL becomes a
JSON transport, so that a `url`-only or combined transport can be tested
against a homeserver that does not advertise one yet. The settings modal
shows each LiveKit room's role instead of a never-populated isLocal flag.

On the SDK the participation options take a whole Transport for the override and the fallback instead of two LiveKit service URLs, which also takes the last LiveKit knowledge out of transport discovery.

(cherry picked from commit d3eb40db0bcf7370418c4948049b3eac176bbdc1)

sdk/src/api.ts

@@ -110,10 +110,13 @@ export interface RTCParticipationOptions {
   timings?: Partial<SessionTimings>;
   /** Limits on what is published; LiveKit's defaults otherwise. */
   mediaQuality?: MediaQuality;
-  /** Use this transport instead of asking the homeserver. */
-  transportUrl?: string;
-  /** Use this transport when the homeserver advertises none. */
-  fallbackTransportUrl?: string;
+  /**
+   * Use this transport instead of asking the homeserver. Any shape the
+   * backend serves: for LiveKit a `url`, a `livekit_service_url` or both.
+   */
+  transport?: Transport;
+  /** Use this transport when the homeserver advertises none of the backend's type. */
+  fallbackTransport?: Transport;
   /**
    * What carries the media. LiveKit, configured from the options above, when
    * left out; see `createLivekitBackend` for building one with other options.
@@ -265,9 +268,6 @@ export interface RTCMember {
    * against `backendIdentities`, not this.
    */
   rtcBackendIdentity: string;
-  userId: string;
-  deviceId: string;
-  /** The membership's own id; what the Matrix 2.0 identity is derived from. */
   /**
    * Every identity this member may publish under on its transport: the
    * participant identity the SFU sees, and the sender of its data packets.
@@ -277,6 +277,9 @@ export interface RTCMember {
    * Opaque to a host.
    */
   backendIdentities: readonly string[];
+  userId: string;
+  deviceId: string;
+  /** The membership's own id; what the Matrix 2.0 identity is derived from. */
   memberId: string;
   /** Which transport this member is on; undefined when the membership has none. */
   transport$: Behavior<TransportMetadata | undefined>;