Add MQTT option to allow high rate for a time

[larsalthof]

The Feature

There are situations where a higher than normal rate of water consumption is needed, e.g. Watering the garden or filling the tub
Currently there is a risk of triggering the “rate too high” error or alternatively risk of water damage by increasing the allowed rate.

It would be nice to have the option of allowing a higher rate for a while through MQTT