code: func (c *Client) UpsertTunnelConnection(conn services.TunnelConnection) error {
  	data, err := services.MarshalTunnelConnection(conn)
  	if err != nil {
  		return trace.Wrap(err)
  	}
  	args := &upsertTunnelConnectionRawReq{
  		TunnelConnection: data,
  	}
  	_, err = c.PostJSON(c.Endpoint("tunnelconnections"), args)
  	return trace.Wrap(err)
  }
docs: // UpsertTunnelConnection upserts tunnel connection