Update SDK to be consumed by Element Call's CallViewModel

Update the public API to export the primitives and operators the call
model needs, and change `LocalMediaInputs` from observable flags to
immediate booleans with imperative setters. Add session timings, media
quality and capture settings as configuration options, and allow the
host to override the transport discovery with explicit URLs.

sdk/dev/main.ts

@@ -12,13 +12,7 @@ Please see LICENSE in the repository root for full details.
  */
 
 import { logger } from "matrix-js-sdk/lib/logger";
-import {
-  BehaviorSubject,
-  combineLatest,
-  type Observable,
-  of,
-  switchMap,
-} from "rxjs";
+import { combineLatest, type Observable, of, switchMap } from "rxjs";
 import {
   constant,
   createMatrixRTCClient,
@@ -71,17 +65,16 @@ async function start(
     const room = await joinRoom(client, roomIdOrAlias);
 
     const scope = new ObservableScope();
-    const microphoneEnabled$ = new BehaviorSubject(true);
-    const cameraEnabled$ = new BehaviorSubject(true);
     const rtcClient = createMatrixRTCClient(
       scope,
       client,
       room,
       {
-        microphoneEnabled$,
-        cameraEnabled$,
+        microphoneEnabled: true,
+        cameraEnabled: true,
         audioInputDeviceId$: constant(undefined),
         videoInputDeviceId$: constant(undefined),
+        audioOutputDeviceId$: constant(undefined),
         videoProcessor$: constant(undefined),
       },
       {
@@ -98,8 +91,12 @@ async function start(
     showMembers(scope, rtcClient);
     rtcClient.join();
 
-    toggle(buttons.microphone, microphoneEnabled$);
-    toggle(buttons.camera, cameraEnabled$);
+    toggle(buttons.microphone, async (enabled) =>
+      rtcClient.setMicrophoneEnabled(enabled),
+    );
+    toggle(buttons.camera, async (enabled) =>
+      rtcClient.setCameraEnabled(enabled),
+    );
     buttons.leave.hidden = false;
     buttons.leave.onclick = (): void => {
       rtcClient.leave();
@@ -114,14 +111,16 @@ async function start(
   }
 }
 
+/** A pressed button means the source is on; the SDK says what it could do. */
 function toggle(
   button: HTMLButtonElement,
-  enabled$: BehaviorSubject<boolean>,
+  set: (enabled: boolean) => Promise<boolean>,
 ): void {
   button.hidden = false;
   button.onclick = (): void => {
-    enabled$.next(!enabled$.value);
-    button.ariaPressed = String(enabled$.value);
+    void set(button.ariaPressed !== "true").then((enabled) => {
+      button.ariaPressed = String(enabled);
+    });
   };
 }