Add ability to configure topic prefix instead of hardcoded "glow"

[photomoose]

My Hildebrand Glow IHD publishes messages with a topic name prefix of "energy" instead of "glow".

I manually edited the data_topic variable sensor.py on my local installation and the IHD was successfully found. (See https://github.com/megakid/ha_hildebrand_glow_ihd_mqtt/blob/main/custom_components/hildebrand_glow_ihd_mqtt/sensor.py#L283)

Could this be made into a configuration setting?

[megakid]

Is this a new IHD? Or did you manually change it? I could expose this as a config option for sure.

[photomoose]

@megakid this is the IHD I received from E.ON - the hardware version, as reported in the STATE topic, is GLOW-IHD-01-1v4-SMETS2.

[RexNoctis]

Fantastic, thanks for the update!