Add timestamp in MQTT shower message

[proddy]

From the discussion #1328 started by @sciurius

he said in HA we use the last-updated property of the sensor to determine the timestamp. Sometimes it's not accurate and would be nicer to add the timestamp to the shower_data MQTT payload which is persisted.

[proddy]

@MichaelDvP said:

"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]

I think time in HH:MM:SS is universal and ok. It's just for displaying in the Home Assistant dashboard.

[sciurius]

A timestamp (seconds since epoch) would avoid timezone issues. Otherwise "2023-10-14T18:46:44+0200" is ok.

[proddy]

@MichaelDvP shall you add or I?

[MichaelDvP]

For the publish it's only

                        time_t now = time(nullptr);
                        if (now > 1576800000) { // year 2020
                            doc["timestamp"] = now; // if needed
                            tm *   tm_ = localtime(&now);
                            char dt[25];
                            strftime(dt, sizeof(dt), "%FT%T%z", tm_);
                            doc["time"] = dt;
                        }

but for the HA config it's better you add it to test and choose the right types.

[proddy]

thanks, I'll add and do a PR now. Along with #1323