Add a page template func

Fixes #9339

resources/page/pagegroup.go

@@ -159,12 +159,7 @@ func (p Pages) GroupBy(ctx context.Context, key string, order ...string) (PagesG
 		case reflect.StructField:
 			fv = ppv.Elem().FieldByName(key)
 		case reflect.Method:
-			var args []reflect.Value
-			fn := hreflect.GetMethodByName(ppv, key)
-			if fn.Type().NumIn() > 0 && fn.Type().In(0).Implements(hreflect.ContextInterface) {
-				args = []reflect.Value{reflect.ValueOf(ctx)}
-			}
-			fv = fn.Call(args)[0]
+			fv = hreflect.CallMethodByName(ctx, key, ppv)[0]
 		}
 		if !fv.IsValid() {
 			continue