Before this fix, the application was simply crashing during execution
when connection to redis was failing.
Now, it is correctly handled with failing promises and logs have been
enabled to clearly see the problem
Before this fix, the redirection URL was stored in the user session,
but this has a big drawback since user could open several pages in
browser and thus override the redirection URL leading the user to
be incorrectly redirected.
Clement Michaud