Add timestamp in MQTT shower message

[sciurius]

The shower MQTT message is {"duration":XXX}. Would it be possible to add the time stamp?
In HA, the last-updated property is not very stable.

[MichaelDvP]

If the esp32-RTC isproper set by NTP, thermostat or manual we can add it.
Do you need timestamp or a time-string (or both)? Of shower end or start/end?
e.g.

{"duration":600, 
"timestamp": 1697294490,
"time":"2023-10-14T16:42:07"
}

[proddy]

created an enhancement #1329