chore: Use onRoomState to monitor group call creation and member join and leave.

lib/src/client.dart

@@ -1098,6 +1098,8 @@ class Client extends MatrixApi {
 
   final CachedStreamController<Event> onGroupMember = CachedStreamController();
 
+  final CachedStreamController<Event> onRoomState = CachedStreamController();
+
   /// How long should the app wait until it retrys the synchronisation after
   /// an error?
   int syncErrorTimeoutSec = 3;

lib/src/room.dart

@@ -197,6 +197,8 @@ class Room {
     }
 
     (states[state.type] ??= {})[stateKey] = state;
+
+    client.onRoomState.add(state);
   }
 
   /// ID of the fully read marker event.

lib/src/voip/voip.dart

@@ -68,9 +68,12 @@ class VoIP {
     client.onAssertedIdentityReceived.stream
         .listen((event) => _handleEvent(event, onAssertedIdentityReceived));
 
-    client.onGroupCallRequest.stream.listen((event) {
-      Logs().v('[VOIP] onGroupCallRequest: type ${event.toJson()}.');
-      onRoomStateChanged(event);
+    client.onRoomState.stream.listen((event) {
+      if (event.type == EventTypes.GroupCallMemberPrefix ||
+          event.type == EventTypes.GroupCallPrefix) {
+        Logs().v('[VOIP] onRoomState: type ${event.toJson()}.');
+        onRoomStateChanged(event);
+      }
     });
 
     client.onToDeviceEvent.stream.listen((event) {