I'm not sure if we should include the combine_keys now in a release just to break it again in another release. But I guess yeah, it makes things much easier logistically. So feel free to ignore me. :)

Yeah, it's a bit frustrating :). I suppose we could do an intermediate PR which used an existing error code, then swap it for a new one in the major release. Or we could remove combine_keys before this release, and reintroduce it in the next major one.

But I think this route is probably the most useful one even if it's a bit messy.