Control my heating pump with a temp sensor

Configuration
7

I normally start with the example provided in the docs. So starting w/ Generic Thermostat there is a minimum amount of data needed to configure it;

# Example configuration.yaml entry
climate:
  - platform: generic_thermostat
    name: Heatpump
    heater: switch.heat_pump
    target_sensor: sensor.study_temperature

As you can see, it is pretty basic. The temperature sensor in the target room. Next we have the switch. As mentioned by @stomko, that could be a relay, but it can also be the current heat pump thermostat inside a Template Switch. So in effect, you have a HA thermostat controlling the heat pump thermostat with two settings. And you get to choose if the HA switch off is actually off or just a lower setpoint. Start with the example in the docs (have taken a stab in the dark)

# Example configuration.yaml entry
switch:
  - platform: template
    switches:
      heat_pump:
        value_template: "{{ is_state_attr('climate.heat_pump', 'hvac_action','heating') }}"
        turn_on:
          service: climate.set_temperature
          target:
            entity_id: climate.heat_pump
           data:
            temperature: 25
        turn_off:
          service: climate.set_temperature
          target:
            entity_id: climate.heat_pump
          data:
            temperature: 15