Consider moving validity.c stuff to common or server
In #41636 Marko said:
Reply To cazfi
If you are implementing functionality like that to server, you may need functions already existing in validity.c -> maybe we should move it to common or server? If I recall correctly, it has no dependencies to other ruledit, or even tools, code.
I think it has changed since this ticket was created, in a way that it's now more ruledit specific.