add methods

src/server/service/file-uploader/uploader.js

@@ -61,6 +61,17 @@ class Uploader {
     return false;
   }
 
+  /**
+   * Whether to redirect to an external signed url.
+   */
+  isReferSignedUrl() {
+    return false;
+  }
+
+  issueSignedUrl() {
+    throw new Error('Implement this');
+  }
+
   /**
    * Respond to the HTTP request.
    * @param {Response} res