[Protocol v7] Remote unpublish & expose permissions (#101)

* fix

* impl

* oldPermissions

* mods

lib/src/internal/events.dart

@@ -194,6 +194,15 @@ class SignalLocalTrackPublishedEvent with SignalEvent, InternalEvent {
   });
 }
 
+@internal
+class SignalTrackUnpublishedEvent with SignalEvent, InternalEvent {
+  final String trackSid;
+
+  const SignalTrackUnpublishedEvent({
+    required this.trackSid,
+  });
+}
+
 @internal
 class SignalRoomUpdateEvent with SignalEvent, InternalEvent {
   final lk_models.Room room;