- xadd(+Redis, +Key, ?Id, +Data:dict) is det
- Add a message to a the stream Key on Redis. The length of the stream
can be capped using the xstream_set/3 option
maxlen(Count). If Id is unbound, generating the id is left to the server and Id is unified with the returned id. The returned id is a string consisting of the time stamp in milliseconds and a sequence number. See Redis docs for details.