Add config to send session membership state events (#2460)

If not set, legacy call membership state events are sent instead.
Even if set, legacy events are sent in rooms with active legacy calls.

---------

Co-authored-by: Timo <16718859+toger5@users.noreply.github.com>

src/config/ConfigOptions.ts

@@ -65,11 +65,21 @@ export interface ConfigOptions {
   };
 
   /**
-   * Allow to join a group calls without audio and video.
-   * TEMPORARY: Is a feature that's not proved and experimental
+   * TEMPORARY experimental features.
    */
   features?: {
-    feature_group_calls_without_video_and_audio: boolean;
+    /**
+     * Allow to join group calls without audio and video.
+     */
+    feature_group_calls_without_video_and_audio?: boolean;
+    /**
+     * Send device-specific call session membership state events instead of
+     * legacy user-specific call membership state events.
+     * This setting has no effect when the user joins an active call with
+     * legacy state events. For compatibility, Element Call will always join
+     * active legacy calls with legacy state events.
+     */
+    feature_use_device_session_member_events?: boolean;
   };
 
   /**

src/rtcSessionHelpers.ts

@@ -108,10 +108,17 @@ export async function enterRTCSession(
 
   // right now we assume everything is a room-scoped call
   const livekitAlias = rtcSession.room.roomId;
+  const useDeviceSessionMemberEvents =
+    Config.get().features?.feature_use_device_session_member_events;
   rtcSession.joinRoomSession(
     await makePreferredLivekitFoci(rtcSession, livekitAlias),
     makeActiveFocus(),
-    { manageMediaKeys: encryptMedia },
+    {
+      manageMediaKeys: encryptMedia,
+      ...(useDeviceSessionMemberEvents !== undefined && {
+        useLegacyMemberEvents: !useDeviceSessionMemberEvents,
+      }),
+    },
   );
 }