function getOAuthService(user) {
  const properties = PropertiesService.getScriptProperties();
  const private_key = properties.getProperty("private_key").replace(/\\n/g, "\n");
  const client_email = properties.getProperty("client_email");

  return OAuth2.createService('Service Account')
    .setTokenUrl('https://accounts.google.com/o/oauth2/token')
    .setPrivateKey(private_key)
    .setIssuer(client_email)
    .setScope('openid');
}