Merge branch '932-confidential-issue' into 'master'

Resolve "Synchronisation of AlekSIS and Django groups causes permissions issues"

Closes #932

See merge request !1453

CHANGELOG.rst

@@ -60,6 +60,7 @@ Fixed
 * [Dev] Foreign keys to ExtensiblePolymorphicModel types were using the wrong manager.
 * [Dev] Allow activating more frequent polling for Celery task progress.
 * [OIDC] Custom additional claims were not present in userinfo 
+* Synchronisation of AlekSIS and Django groups caused permissions issues
 
 Removed
 ~~~~~~~

aleksis/core/models.py

@@ -577,20 +577,25 @@ class Group(SchoolTermRelatedExtensibleModel):
 
         if force or dirty:
             # Synchronise group to Django group with same name
-            dj_group, _ = DjangoGroup.objects.get_or_create(name=self.name)
-            dj_group.user_set.set(
-                list(
-                    self.members.filter(user__isnull=False)
-                    .values_list("user", flat=True)
-                    .union(self.owners.filter(user__isnull=False).values_list("user", flat=True))
+            dj_group = self.django_group
+            if dj_group:
+                dj_group.user_set.set(
+                    list(
+                        self.members.filter(user__isnull=False)
+                        .values_list("user", flat=True)
+                        .union(
+                            self.owners.filter(user__isnull=False).values_list("user", flat=True)
+                        )
+                    )
                 )
-            )
-            dj_group.save()
+                dj_group.save()
 
     @property
     def django_group(self):
         """Get Django group for this group."""
-        dj_group, _ = DjangoGroup.objects.get_or_create(name=self.name)
+        dj_group = None
+        if not self.school_term or self.school_term == SchoolTerm.current:
+            dj_group, _ = DjangoGroup.objects.get_or_create(name=self.name)
         return dj_group