Resolve "Frontend for Models"

Closes #1 (closed)

aleksis/apps/lesrooster/apps.py

@@ -40,8 +40,21 @@ class DefaultConfig(AppConfig):
             )
             signals.m2m_changed.connect(
                 m2m_changed_handler,
-                sender=model,
+                sender=model.teachers.through,
             )
             signals.pre_delete.connect(pre_delete_handler, sender=model)
 
+        signals.m2m_changed.connect(
+            m2m_changed_handler,
+            sender=Lesson.rooms.through,
+        )
+        signals.m2m_changed.connect(
+            m2m_changed_handler,
+            sender=Supervision.rooms.through,
+        )
+        signals.m2m_changed.connect(
+            m2m_changed_handler,
+            sender=Substitution.rooms.through,
+        )
+
         signals.post_save.connect(create_time_grid_for_new_validity_range, sender=ValidityRange)