DIY Light with integrated On / Off Switch

Good Morning
my name is Martin and I am from Switzerland. I have just started with diyHue and I think it’s fantastic, so really, well done guys!

I am currently developing my first “light”. My plan is to replace one of our bluetooth gardena irrigation controllers with an esp acting as a light / switch to turn it on / off. What I would like to integrate is a button connected to the esp, that could start the watering manually for 30 min.

My questions is, how can I tell the server that I switched it on locally? Is there a way to let the server / diyHue know, that the status changed? Or would the concept be to have 2 functions, a button and a ON/ OFF device on one esp at the same time? Also, I could not find it in the docs, probably to old to find it…

Any thoughts, ideas would be appreciated.