✨(api) add CRUD for mailbox manager MailDomain models

Add create,list,retrieve and delete actions for MailDomain model.

src/backend/mailbox_manager/api/permissions.py

@@ -0,0 +1,12 @@
+"""Permission handlers for the People mailbox manager app."""
+
+from core.api import permissions as core_permissions
+
+
+class AccessPermission(core_permissions.IsAuthenticated):
+    """Permission class for access objects."""
+
+    def has_object_permission(self, request, view, obj):
+        """Check permission for a given object."""
+        abilities = obj.get_abilities(request.user)
+        return abilities.get(request.method.lower(), False)