code: func (s *PresenceService) UpsertTrustedCluster(trustedCluster services.TrustedCluster) (services.TrustedCluster, error) {
  	if err := trustedCluster.CheckAndSetDefaults(); err != nil {
  		return nil, trace.Wrap(err)
  	}
  	value, err := services.GetTrustedClusterMarshaler().Marshal(trustedCluster)
  	if err != nil {
  		return nil, trace.Wrap(err)
  	}
  	_, err = s.Put(context.TODO(), backend.Item{
  		Key:     backend.Key(trustedClustersPrefix, trustedCluster.GetName()),
  		Value:   value,
  		Expires: trustedCluster.Expiry(),
  		ID:      trustedCluster.GetResourceID(),
  	})
  	if err != nil {
  		return nil, trace.Wrap(err)
  	}
  	return trustedCluster, nil
  }
docs: // UpsertTrustedCluster creates or updates a TrustedCluster in the backend.