New relay sync mode where all additional switches follow the first one

[foxel]

The new sync mode (named "Switch #0 controls other switches" in UI) means that if switch #0 changes other switches will sync to it but not vice-versa

This scheme come to my mind as a solution to a case when I want to have a switch turning all the relays ON and OFF in one click, but be able to control the secondary switches independently.

My UCs:

1. I have a set of high-power and low-power lights for my desk, the low-power one is controlled by motion detection thru home-assistant, and i have a button which controls the high-power one. With this sync mode when i press this button I get all the lights on or off, and motion detection controls only one light.
2. Over the dinner table I have a chandelier with two groups of bulbs, the chendelier is controlled thru 433 MHz RF remote on the wall and most common use of this is to turn the whole chendelier on/off, I could connect all the bulbs into one group but i still want to be able to set the lights to some dimmer state from my phone. This is also acheived with the synck mode suggested.

Do you think this is a valuable addition to the firmware?

[mcspr]

I think this matches nicely with other logic here.

And maybe one could describe several of such groups on one device?
e.g. 8 switch board, switch#1 controls first 3 switches, switch#4 controls last 3 in a similar manner.
idk though how this can be described in the config yet. only rough idea:
relayMode reuse relay mode from this option
relaySyncMap<relayID> bitmap of switches that are synchronized with the main one when it changes, but independent otherwise. e.g. relaySyncMap0 => 01110000, relaySyncMap4 => 00000111 for my example.

[xoseperez]

Nice one.

This could be the answer for #1062. Still, I'd prefer to merge this as is and the look for a more general solution.