message: avoid making a copy from vectorBody
diff: @@ -103,7 +103,7 @@ AccessToken ClientSecretCredential::GetToken(
  throw AuthenticationException(errorMsg.str());
  }
  - auto const responseBodyVector = response->GetBody();
  + auto const& responseBodyVector = response->GetBody();
  std::string responseBody(responseBodyVector.begin(), responseBodyVector.end());
  // TODO: use JSON parser.
  