code: function sendToClient (message, client) {
    return new Promise((resolve, reject) => {
      try {
        client.send(JSON.stringify(message), (e) => {
          if (e) {
            logger.error(`could not send rtm message to client`, e)
            return reject(e)
          }
        })
      } catch (e) {
        logger.error(`could not send rtm message to client`, e)
        return reject(e)
      }
  
      resolve()
    })
  }
docs: sends the given message to the given client