Restore Order.add_record, used by uncloud_pay tests

uncloud_django_based/uncloud/uncloud_pay/models.py

@@ -476,6 +476,15 @@ class Order(models.Model):
     def recurring_price(self):
         return reduce(lambda acc, record: acc + record.recurring_price, self.records, 0)
 
+    # Used by uncloud_pay tests.
+    def add_record(self, one_time_price, recurring_price, description):
+      OrderRecord.objects.create(order=self,
+              one_time_price=one_time_price,
+              recurring_price=recurring_price,
+              description=description)
+
+
+
 class OrderRecord(models.Model):
     """
     Order records store billing informations for products: the actual product