Fixed #30941 -- Reverted "Simplified AuthenticationMiddleware a bit."

This reverts commit 2f010795e6.

django/contrib/auth/middleware.py

@@ -1,5 +1,3 @@
-from functools import partial
-
 from django.contrib import auth
 from django.contrib.auth import load_backend
 from django.contrib.auth.backends import RemoteUserBackend
@@ -8,6 +6,12 @@ from django.utils.deprecation import MiddlewareMixin
 from django.utils.functional import SimpleLazyObject
 
 
+def get_user(request):
+    if not hasattr(request, '_cached_user'):
+        request._cached_user = auth.get_user(request)
+    return request._cached_user
+
+
 class AuthenticationMiddleware(MiddlewareMixin):
     def process_request(self, request):
         assert hasattr(request, 'session'), (
@@ -16,7 +20,7 @@ class AuthenticationMiddleware(MiddlewareMixin):
             "'django.contrib.sessions.middleware.SessionMiddleware' before "
             "'django.contrib.auth.middleware.AuthenticationMiddleware'."
         )
-        request.user = SimpleLazyObject(partial(auth.get_user, request))
+        request.user = SimpleLazyObject(lambda: get_user(request))
 
 
 class RemoteUserMiddleware(MiddlewareMixin):