I have a OpenTherm Gateway via ethernet and opentherm_gw integrated in Home Assistant. It is now possible to change the desired temperature in the living room. That’s OK. Now I want to change the desired temperature in a automation: every morning at 08:30 when there is somebody in the house, the temperature to 19 °C, every evening at 22:00, 22:30 etc. the temperature to 15 °C.
There are services for changes, but no service for changing the desired temperature. I have studied services.yaml  but I am not yet capable of writing my own service for this.
How can I send the desired temperature to the heater?