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.

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

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,
+      }),
+    },
   );
 }