Upgrade to Django 5.2 LTS

Author: ihalaij1

requirements.txt

@@ -1,5 +1,5 @@
-Django ~= 4.2.3
-git+https://github.com/apluslms/django-essentials.git@1.6.0#egg=django-essentials==1.6.0
+Django ~= 5.2.13
+git+https://github.com/apluslms/django-essentials.git@1.7.0#egg=django-essentials
 requests >= 2.28.0, < 3
 PyYAML ~= 6.0.0
 docutils ~= 0.17.1

util/http.py

@@ -125,7 +125,7 @@ def not_modified_since(request, exercise):
         or not exercise.get('cacheable', True)
     ):
         return False
-    time = parse_http_date_safe(request.META.get('HTTP_IF_MODIFIED_SINCE'))
+    time = parse_http_date_safe(request.headers.get('if-modified-since'))
     return time and time >= exercise['mtime']