ENH Use FieldValidator for FormFields

code/Forms/UploadField.php

@@ -324,7 +324,7 @@ public function performDisabledTransformation()
      * @param Validator $validator
      * @return bool
      */
-    public function validate($validator)
+    protected function validateField(Validator $validator, ValidationResult $result): bool
     {
         $maxFiles = $this->getAllowedMaxFileNumber();
         $count = count($this->getItems() ?? []);