code: func (s *PresenceService) UpsertTunnelConnection(conn services.TunnelConnection) error {
  	if err := conn.CheckAndSetDefaults(); err != nil {
  		return trace.Wrap(err)
  	}
  	value, err := services.MarshalTunnelConnection(conn)
  	if err != nil {
  		return trace.Wrap(err)
  	}
  	_, err = s.Put(context.TODO(), backend.Item{
  		Key:     backend.Key(tunnelConnectionsPrefix, conn.GetClusterName(), conn.GetName()),
  		Value:   value,
  		Expires: conn.Expiry(),
  		ID:      conn.GetResourceID(),
  	})
  	if err != nil {
  		return trace.Wrap(err)
  	}
  	return nil
  }
docs: // UpsertTunnelConnection updates or creates tunnel connection