Can't use anything else than "org.xwiki.contrib" prefix for group id of non core artifacts

XCOMMONS-979 ended up forbidding everything but "org.xwiki.contrib" prefix for anything having xwiki-commons as parent (everything which is not standard commons, rendering, platform or enterprise). It was actually the goal but did not had in mind other use cases that extensions registered on https://github.com/xwiki-contrib/.

Workaround is to disable this enforcer or use https://github.com/xwiki-contrib/parent (which disable this enforcer).