code: func (s *PresenceService) DeleteTunnelConnections(clusterName string) error {
  	if clusterName == "" {
  		return trace.BadParameter("missing cluster name")
  	}
  	startKey := backend.Key(tunnelConnectionsPrefix, clusterName)
  	err := s.DeleteRange(context.TODO(), startKey, backend.RangeEnd(startKey))
  	return trace.Wrap(err)
  }
docs: // DeleteTunnelConnections deletes all tunnel connections for cluster