Simplify local transport code

As of the removal of 'Legacy' mode, there can no longer be a difference between the transport you advertise in your membership and the transport you publish media on, so the local transport code can be simplified considerably. For instance, the function which gets the local transport can simply return a promise rather than being reactive.

I kept the local transport as an Observable in other modules so that they could easily be tested with existing marble tests.

src/state/CallViewModel/remoteMembers/ConnectionManager.ts

@@ -7,7 +7,14 @@ Please see LICENSE in the repository root for full details.
 */
 
 import { type LivekitTransportConfig } from "matrix-js-sdk/lib/matrixrtc";
-import { combineLatest, map, of, switchMap } from "rxjs";
+import {
+  combineLatest,
+  map,
+  type Observable,
+  of,
+  switchMap,
+  startWith,
+} from "rxjs";
 import { type Logger } from "matrix-js-sdk/lib/logger";
 import { type RemoteParticipant } from "livekit-client";
 import { type CallMembershipIdentityParts } from "matrix-js-sdk/lib/matrixrtc/EncryptionManager";
@@ -19,8 +26,8 @@ import { generateItemsWithEpoch } from "../../../utils/observable.ts";
 import { areLivekitTransportsEqual } from "./MatrixLivekitMembers.ts";
 import { type ConnectionFactory } from "./ConnectionFactory.ts";
 import {
-  isLocalTransportWithSFUConfig,
-  type LocalTransportWithSFUConfig,
+  isLocalTransport,
+  type LocalTransport,
 } from "../localMember/LocalTransport.ts";
 import { type SFUConfig } from "../../../livekit/openIDSFU.ts";
 
@@ -78,7 +85,7 @@ export class ConnectionManagerData {
 interface Props {
   scope: ObservableScope;
   connectionFactory: ConnectionFactory;
-  localTransport$: Behavior<LocalTransportWithSFUConfig | null>;
+  localTransport$: Observable<LocalTransport>;
   remoteTransports$: Behavior<Epoch<LivekitTransportConfig[]>>;
 
   logger: Logger;
@@ -121,6 +128,11 @@ export function createConnectionManager$({
   const logger = parentLogger.getChild("[ConnectionManager]");
   // TODO logger: only construct one logger from the client and make it compatible via a EC specific sing
 
+  const localTransportAsArray$ = localTransport$.pipe(
+    map((transport) => [transport]),
+    startWith([]),
+  );
+
   /**
    * All transports currently managed by the ConnectionManager.
    *
@@ -130,16 +142,12 @@ export function createConnectionManager$({
    * externally this is modified via `registerTransports()`.
    */
   const localAndRemoteTransports$: Behavior<
-    Epoch<(LivekitTransportConfig | LocalTransportWithSFUConfig)[]>
+    Epoch<(LivekitTransportConfig | LocalTransport)[]>
   > = scope.behavior(
-    combineLatest([remoteTransports$, localTransport$]).pipe(
+    combineLatest([localTransportAsArray$, remoteTransports$]).pipe(
       // Combine local and remote transports into one transport array
       // and set the forceOldJwtEndpoint property on the local transport
-      map(([remoteTransports, localTransport]) => {
-        let localTransportAsArray: LocalTransportWithSFUConfig[] = [];
-        if (localTransport) {
-          localTransportAsArray = [localTransport];
-        }
+      map(([localTransportAsArray, remoteTransports]) => {
         const dedupedRemote = removeDuplicateTransports(remoteTransports.value);
         const remoteWithoutLocal = dedupedRemote.filter(
           (transport) =>
@@ -170,7 +178,7 @@ export function createConnectionManager$({
         "ConnectionManager connections$",
         function* (transports) {
           for (const transport of transports) {
-            if (isLocalTransportWithSFUConfig(transport)) {
+            if (isLocalTransport(transport)) {
               // This is the local transport; only the `LocalTransportWithSFUConfig` has a `sfuConfig` field.
               yield {
                 keys: [