With this change, URLs for forum listings are now available. This
includes URLs like /news or /projects/games. Each of them show a
(currently empty) forum index.
Note that URLs that are not linked to in the forum index, namely URLs
for forums that have children (eg. /forum/news), are still accessible. We
could ban this by raising ValidationError if the forum has a non-empty
[sub_forums] attribute but displaying all subjects feels better.
URLs that point to /forum, but do not name a sub-forum and are not of
the form of a topic URL produce 404 errors.
Lephe
d1a8333cae
