Method StringSetter

cpp/src/arrow/filesystem/s3fs.cc:1388–1393

 private:
  static Setter StringSetter(void (ObjectRequest::*req_method)(Aws::String&&)) {
    return [req_method](const std::string& v, ObjectRequest* req) {
      (req->*req_method)(ToAwsString(v));
      return Status::OK();
    };
  }

  static Setter DateTimeSetter(
      void (ObjectRequest::*req_method)(Aws::Utils::DateTime&&)) {