Features: 1) Add update_order_products_statuses method for bulk updating product statuses; 2) Wrap order creation logic in atomic transaction to ensure integrity.

Fixes: 1) Add missing `transaction` import in `core/models.py`.

Extra: 1) Refactor order product status updates to use the new method; 2) Enhance readability and maintainability of order processing logic.

core/models.py

@@ -9,6 +9,7 @@ from django.contrib.postgres.indexes import GinIndex
 from django.core.cache import cache
 from django.core.exceptions import BadRequest, ValidationError
 from django.core.validators import MaxValueValidator, MinValueValidator
+from django.db import transaction
 from django.db.models import (
     CASCADE,
     PROTECT,
@@ -1617,9 +1618,10 @@ class Order(ExportModelOperationsMixin("order"), NiceModel):  # type: ignore [mi
             case "balance":
                 if order.user.payments_balance.amount < amount:
                     raise NotEnoughMoneyError(_("insufficient funds to complete the order"))
+                with transaction.atomic():
                     order.status = "CREATED"
                     order.buy_time = timezone.now()
-                order.order_products.all().update(status="DELIVERING")
+                    order.update_order_products_statuses("DELIVERING")
                     order.save()
                     return order
             case "payment":
@@ -1708,6 +1710,9 @@ class Order(ExportModelOperationsMixin("order"), NiceModel):  # type: ignore [mi
             self.status = "FINISHED"
             self.save()
 
+    def update_order_products_statuses(self, status: str = "PENDING"):
+        self.order_products.update(status=status)
+
     def bulk_add_products(self, products: list[dict[str, Any]]):
         for product in products:
             self.add_product(