Previously we had a lot of hardcoded contest information in the
templates. Name, ruleset and number of contest are now all taken from
the currently active contest and rendered into the templates. Instead of
an URL containing the current contest name, we just use a generic
/contest/. The API will no longer use "the contest with id=1", but the
currently active contest as well.
The currently active contest is - for now - the contest with the latest
deadline.
url() is no longer available, has to be replaced with path() or
re_path(). For proper include() we also need an app_name specified in
the urls.py we're including.