code: func (a *AuthServer) GetDomainName() (string, error) {
  	clusterName, err := a.GetClusterName()
  	if err != nil {
  		return "", trace.Wrap(err)
  	}
  	return clusterName.GetClusterName(), nil
  }
docs: // GetDomainName returns the domain name that identifies this authority server.
  // Also known as "cluster name"