code: function sendDirectToUser(content, username) {
      return getDirectMessageRoomId(username)
          .then((rid) => sendToRoomId(content, rid));
  }
docs: Prepare and send string/s to a user in a DM.
  @param content   Accepts message text string or array of strings.
  @param username  Name to create (or get) DM for room ID to use in send.