How to Override the Default Universe Domain

  google::cloud::Options options;

  // AddUniverseDomainOption interrogates the UnifiedCredentialsOption, if set,
  // in the provided Options for the Universe Domain associated with the
  // credentials and adds it to the set of Options.
  // If no UnifiedCredentialsOption is set, GoogleDefaultCredentials are used.
  auto ud_options = google::cloud::AddUniverseDomainOption(std::move(options));

  if (!ud_options.ok()) throw std::move(ud_options).status();
  auto ud_client = google::cloud::servicedirectory_v1::LookupServiceClient(
      google::cloud::servicedirectory_v1::MakeLookupServiceConnection(
          *ud_options));