Add mapping for json payload keys

[ms49434]

This mod will simplify the integration of this driver into an existing setup.

I already have a working setup with a Hichi IR Reader, OpenDTU, Zero Export, Node-Red, Mosquitto and a Cerbo GX. To add the Hichi (Tasmota) to Venus OS.
Renaming the keys and the topic wasn't an option because of the existing setup.

A new (optional) section [MAP] in config.ini file allows you to map the keys used in your environment (i.e. power => Power_curr) and publish them to dbus using the dbus key names.

Example:
...
[MAP]
power = Power_curr (Read the key Power_curr for the power value)
energy_forward = Total_in
energy_reverse = Total_out

List of available keys:
grid
power
voltage
current
frequency
L1
L2
L3
power_L1
power_L2
power_L3
energy_forward
energy_reverse

[mr-manuel]

Thanks for contributing. I like the idea, but I would make it more flexible and repeat less same code.

1. Like loop through all values set under [MAP], if there are any.
2. Allow nested values like energy_forward = grid/total/out

[peterix99]

Great code! With more keys will be possible to connect a device to Venus OS using Ble, now I have a device (smartshunt) to RasPi running signalk connected by Ble and then to Pizero running Venus OS using your code and mqtt.