Extract permitted params lists

So they can be easily extended by (...wait for it...) _extensions_

pages/app/controllers/refinery/admin/page_parts_controller.rb

@@ -23,9 +23,13 @@ def destroy
 
       protected
         def new_page_part_params
-          params.except(:part_index).permit(:title, :slug, :body, :locale)
+          params.except(:part_index).permit(permitted_new_page_part_params)
         end
 
+      private
+        def permitted_new_page_part_params
+          [:title, :slug, :body, :locale]
+        end
     end
   end
 end

pages/app/controllers/refinery/admin/pages_controller.rb

@@ -91,7 +91,7 @@ def page_params
       end
 
       def new_page_params
-        params.permit(:parent_id, :view_template, :layout_template)
+        params.permit(permitted_new_page_params)
       end
 
       private
@@ -100,10 +100,18 @@ def permitted_page_params
         [
           :browser_title, :draft, :link_url, :menu_title, :meta_description,
           :parent_id, :skip_to_first_child, :show_in_menu, :title, :view_template,
-          :layout_template, :custom_slug, parts_attributes: [:id, :title, :slug, :body, :position]
+          :layout_template, :custom_slug, parts_attributes: permitted_parts_attributes_params
         ]
       end
 
+      def permitted_parts_attributes_params
+        [:id, :title, :slug, :body, :position]
+      end
+
+      def permitted_new_page_params
+        [:parent_id, :view_template, :layout_template]
+      end
+
       def save_and_continue_locals(page)
         nested_url = page.nested_url
         {