bugfix: relax next verification

AUR renders its own 404 Not Found page when a bad route
is encountered. Introducing the previous verification
caused an error in this case when setting a language
while viewing the Not Found page. So, instead of checking
through routes, just make sure that the next parameter
starts with a '/' character, which removes the possibility
of any cross attacks.

+ Removed aurweb.asgi.routes; no longer needed.

Signed-off-by: Kevin Morris <kevr@0cost.org>

test/test_routes.py

@@ -61,7 +61,7 @@ def test_language_invalid_next():
     """ Test an invalid next route at '/language'. """
     post_data = {
         "set_lang": "de",
-        "next": "/BLAHBLAHFAKE"
+        "next": "https://evil.net"
     }
     with client as req:
         response = req.post("/language", data=post_data)