refactor `handle_model` to use private helper methods for generation

actionpack/lib/action_dispatch/routing/polymorphic_routes.rb

@@ -247,15 +247,13 @@ def handle_model(record)
           args  = []
 
           model = record.to_model
-          name = if model.persisted?
+          named_route = if model.persisted?
                           args << model
-                   model.model_name.singular_route_key
+                          get_method_for_string model.model_name.singular_route_key
                         else
-                   @key_strategy.call model.model_name
+                          get_method_for_class model
                         end
 
-          named_route = get_method_for_string name
-
           [named_route, args]
         end