feat(APIv2): optionally allow the selection of additional fields

app/controllers/v2/application_controller.rb

@@ -60,6 +60,8 @@ def rbac_allowed?
     def expand_resource
       # Get the list of fields to be selected from the serializer
       fields = serializer.fields(permitted_params[:parents], resource.one_to_one)
+      # Append a list of additional fields required to render the response, usually RBAC related
+      fields[nil] += extra_fields
 
       # Join with the parents assumed from the route
       scope = join_parents(pundit_scope, permitted_params[:parents])
@@ -107,5 +109,10 @@ def select_fields(fields)
         end
       end
     end
+
+    # Default list of additional fields to be passed to the list of selected fields
+    def extra_fields
+      []
+    end
   end
 end