Return the right ActiveModel::Name on operation

Return the ActiveModel::Name for Op Model Class instead of Op Class

The current file is return ActiveModel::Name with @klass == Thing::Create, thats and operation, and rails responder tries to find and URL for this object that has no routes configure on our rails app.

When we return its parent ActiveModel::Name, its ok, has the right properties and find the path correctly
this return nil is not beautiful but was needed in the case the class has no Namespace