[FR] Time tagging of messages (in the same manner as OpenMQTTGateway)

[ilgrank]

Hi
Some time ago we added a time tagging feature to OpenMQTTGateway
Could it be possible to port this feature to Theengs Gateway?
(I'm talking about the message_unixtimestamp and message_UTCtimestamp options)

Time tagging on ESP32 works perfectly, and helped me discover lots of issues in my setup.
But doing tests on remote ESP32s is quite difficult, and having the same behaviour replicated on Theengs Gateway would speed up implementations greatly (to me at least :)