code: async function syncBrainUsers (robot) {
    try {
      robot.logger.info(`[syncBrainUsers] adding all users to Hubot brain`)
      const allUsers = await robot.adapter.api.users.all()
      const knownUsers = robot.brain.users()
      const addedUsers = []
      for (let user of allUsers) {
        if (knownUsers[user._id]) continue
        robot.brain.userForId(user._id, {
          name: user.username,
          alias: user.alias
        })
        addedUsers.push(user.username)
      }
      return addedUsers
    } catch (err) {
      robot.logger.error('Could not sync user data with bot', err)
    }
  }
docs: Use API user helper to sync RC users with Hubot brain.
  Test with `node docs/snippets syncBrainUsers` from project root.
  @param {Robot} robot        The Hubot instance
  @returns {string|undefined} List of names added