Features: 1) Add validation to ensure category_uuid is present when using include_subcategories flag;

Fixes: 1) Add missing import for `BadRequest` from `django.core.exceptions`;

Extra: 1) Update placeholder method `filter_include_flag` with proper implementation;

core/filters.py

@@ -2,6 +2,7 @@ import json
 import logging
 import uuid
 
+from django.core.exceptions import BadRequest
 from django.db.models import Avg, FloatField, OuterRef, Q, Subquery, Value
 from django.db.models.functions import Coalesce
 from django.utils.http import urlsafe_base64_decode
@@ -121,7 +122,8 @@ class ProductFilter(FilterSet):
                 )
 
     def filter_include_flag(self, queryset, name, value):
-        # just a placeholder method
+        if not self.data.get("category_uuid"):
+            raise BadRequest(_("there must be a category_uuid to use include_subcategories flag"))
         return queryset
 
     def filter_attributes(self, queryset, _name, value):