API: query `patch` param is missing

[SergioGlorias]

From lichess-org/lila#18518 for lichess-org/lila#17744

All update forms have support ?patch=1
If enabled, just need to provide properties to update (no need to input all properties)
Require properties no need add

[ornicar]

Fair enough. I'm just not sure it works as expected for all forms - or that there are valid expectations to make in some cases.

I'm concerned that by documenting it I would be committing to make it work for every POST endpoint, and that it would sometimes be very awkward. Maybe. IDK

[ornicar]

Maybe we just add it where it's been tried and tested first?

[SergioGlorias]

I'm currently using it in the broadcast rounds update and it's working correctly.
I haven't tested it yet; clearing fields might cause problems there.

[ornicar]

I expect issues with embedded fields, array fields, and more. Haven't tested anything.