First draft of the new registration documentation.
The idea is that a POST to the registration URL https://gitlab.common-lisp.net/users returns a redirect to this page, unless the "Referer" header includes some secret. On #lisp minion can be asked about the right URL. Ad 1: well-known (like just "?allow=lisp") or generated; eg. some date-value like "MMMDD-HH", which would give "May09-20:"; Perhaps we can just use the unix-timestamp and have apache compare an integer range?