fix: delete perm on user/group/team deletion

This is done manually using signal because we do not use a foreign key
so we do not have automatically cascade deletion.

permissions/apps.py

@@ -0,0 +1,10 @@
+from django.apps import AppConfig
+
+
+class PermissionsConfig(AppConfig):
+
+    name = 'permissions'
+    verbose_name = 'Permissions'
+
+    def ready(self):
+        import permissions.signals