[5.8] Fixing previous url

[veencel]

Currently, the previous url is set too early in the StartSession middleware.
When the referrer header is missing, the back() call always redirects to the current URL creating a redirect loop.

I think this commit introduced this bug, setting the url after calling the $next callback solves the issue.

[driesvints]

I believe this is indeed the culprit. I was just investigating this myself and think the reversal of the sequence in which these calls were made indeed broke it. But this definitely needs a test or otherwise this will break again.

#27894 (comment)

[driesvints]

Instead of writing this like so in which the next call gets lost in the other call this might be a more obvious approach:

        $response = $next($request);

        $this->storeCurrentUrl($request, $session);
        $this->addCookieToResponse($response, $session);