Automation of setting room temperature

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 [1] but I am not yet capable of writing my own service for this.

How can I send the desired temperature to the heater?

[1] core/services.yaml at b2bcdf7c1928ed88c69ddf100e2e5a8e4fd07cb4 · home-assistant/core · GitHub

Is there a climate entity? According to the opentherm docs, there should be. If so, use the climate services:

Climate - Home Assistant (