[PUI] Fix global login (#6287)

* Global login PUI -> CUI
Fixes #6285

* ensure session is always set

* Check if user is already logged in CUI->PUI

* reduce diff

InvenTree/users/api.py

@@ -3,6 +3,7 @@
 import datetime
 import logging
 
+from django.contrib.auth import get_user, login
 from django.contrib.auth.models import Group, User
 from django.urls import include, path, re_path
 
@@ -242,6 +243,10 @@ class GetAuthToken(APIView):
                 "Created new API token for user '%s' (name='%s')", user.username, name
             )
 
+            # Ensure that the users session is logged in (PUI -> CUI login)
+            if not get_user(request).is_authenticated:
+                login(request, user)
+
             return Response(data)
 
         else: