code: function toMessageBFK(messageState) {
    // if (!hasMessageIdentifier(messageState)) {
    //   return undefined;
    // }
    const md5s = messageState.md5s;
    return [
      trimOrEmpty(messageState.eventID), trimOrEmpty(messageState.eventSeqNo), trimOrEmpty(messageState.eventSubSeqNo),
      trimOrEmpty(messageState.id), trimOrEmpty(messageState.key), trimOrEmpty(messageState.seqNo),
      trimOrEmpty(md5s && md5s.msg), trimOrEmpty(md5s && md5s.userRec), trimOrEmpty(md5s && md5s.rec),
      trimOrEmpty(md5s && md5s.data)
    ].join('|');
  }
docs: Creates a BFK (i.e. Big Fat Key) for the given message state using EVERY available id, key and sequence number property.
  @param {MessageState} messageState - the tracked state of a message
  @returns {string|undefined} an "over-the-top" key for matching purposes