code: func (s *ClusterConfigurationService) GetAuthPreference() (services.AuthPreference, error) {
  	item, err := s.Get(context.TODO(), backend.Key(authPrefix, preferencePrefix, generalPrefix))
  	if err != nil {
  		if trace.IsNotFound(err) {
  			return nil, trace.NotFound("authentication preference not found")
  		}
  		return nil, trace.Wrap(err)
  	}
  	return services.GetAuthPreferenceMarshaler().Unmarshal(item.Value,
  		services.WithResourceID(item.ID), services.WithExpires(item.Expires))
  }
docs: // GetAuthPreference fetches the cluster authentication preferences
  // from the backend and return them.