[AAP-59444] Add metadata to return the AuthenticatorUpdateSerializer to say 'type' is read only (ansible#889)

Adding metadata to the checks for the serializer to make type read-only.

Author: tyraziel

ansible_base/authentication/views/authenticator.py

@@ -37,7 +37,7 @@ def get_serializer(self, *args, **kwargs):
         return super().get_serializer(*args, **kwargs)
 
     def get_serializer_class(self):
-        if self.action in ['update', 'partial_update']:
+        if self.action in ['update', 'partial_update', 'metadata']:
             return AuthenticatorUpdateSerializer
         return super().get_serializer_class()