Make the cluster config settable through ENV or input

[golfvert]

Thanks for the great node, that is helping me a lot in eg. this project https://github.com/golfvert/WIS2-GlobalBroker-NodeRed
I'd like to be able to set "dynamically" the clustering mode.
At the moment, in the above container, I am relying on a redis container on the same bridge network and not in cluster mode.
I'd like to make the redis configuration more ubiquitous.
Typicallly, using an ENV variable for the redis server (and not a static string). This one seems to be doable (I have not tried it yet though).
The cluster mode is a tick box and there seems to be no way to set the tick box through an ENV variable. I am missing something ?
Can the node be updated to cater with this ? Eg through an ENV CLUSTER true/false kind of things. Thanks!