feat: support webhook (#1187)

ui/flutter/lib/api/api.dart

@@ -236,6 +236,11 @@ Future<void> updateExtension(String identity) async {
       () => _client.dio.post("api/v1/extensions/$identity/update"), null);
 }
 
+Future<void> testWebhook(String url) async {
+  return _parse(
+      () => _client.dio.post("api/v1/webhook/test", data: {"url": url}), null);
+}
+
 Future<String> login(LoginReq loginReq) async {
   return _parse(() => _client.dio.post("api/web/login", data: loginReq),
       (data) => data as String);