Require an author for a patch #15

Patches are obviously authored by someone. So not filling out an author is usually a mistake. Chances of that happening should be severely reduced by #13.

It's unclear if we actually want this if we already have #13. In cases where you add a patch for someone else (e.g. to run CI on it when you're reviewing it), but that person has no commitfest account you would then have two options:

1. Not create the patch
2. Assign yourself as author (even though you are not).