Add is_admin field to User model and update related serializers and views

devices/views.py

@@ -30,7 +30,9 @@ class DeviceListCreateAPIView(
     def list(self, request, *args, **kwargs):
         queryset = self.filter_queryset(self.get_queryset())
 
-        if not request.user.is_superuser:
+        if request.user.is_authenticated and not getattr(
+            request.user, "is_admin", False
+        ):
             queryset = queryset.filter(user=request.user)
 
         page = self.paginate_queryset(queryset)