In 1aaf5d08 support was added to lookup the filename when accessing the
/file endpoint and set the Content-Dispatch response header accordingly.
However, that is hidden behind a feature flag as it requires a
potentially costly db lookup. Further, it does not help in prod setups
where the files are served directly from the farm by the webserver.

To solve this, we now append the url-encoded filename to the path (after
the digest), so the webserver can decode this and set the
Content-Dispatch header accordingly.

Proposed-by: Philipp Kern <pkern@debian.org>
Signed-off-by: Felix Moessbauer <felix.moessbauer@siemens.com>