Several ways you can wire your door sill. I guess it should be default 12V input.
1) Not the best, but run the wires under carpet or bottom door sill, tap to the cigarette lighter or fuse box (driver side dashboard after you open door). Always on when you switch on the car.
2) Tap to the footwell lighting. Only on when the footwell also lights on. But at night, will be always on (?).
3) Tap to the door CAN-bus, need to run the wire through the bottom door sill, into door. Only on when door is open, similiar like my door lights above. May need VCDS. And tools to open the door panel. Most labour intensive among all.
If you cut any wires, it may affect warranty for that part/area. In my case, wire plug into CAN-bus, I can pull out and dismantle, to put back original door-reflector.
Damn! sounds sophisticated...