refactor(business): Streamline promo views and data handling

This commit refactors the `business` app's views and serializers to improve efficiency and clarify the logic for handling promo data.

Key changes:
 - **Simplified Query Validation:** The `CompanyPromoListCreateView` now validates query parameters directly within the `get_queryset` method, removing the need for an intermediate `list` method override and instance variables.
- **Optimized Target Updates:** The `PromoDetailSerializer` now correctly handles updates to the `target` field by calling the parent `update` method first and then saving the `target` field specifically. This ensures atomicity and prevents unnecessary model saves.
 - **Improved QuerySet Definition:** The `PromoManager` now defines `with_related_fields` as a tuple to clearly specify the fields for `only()`, making the query more  readable and maintainable.

Author: RandomProgramm3r

promo_code/business/managers.py

@@ -22,29 +22,32 @@ def create_company(self, email, name, password=None, **extra_fields):
 
 
 class PromoManager(django.db.models.Manager):
+    with_related_fields = (
+            'id',
+            'company__id',
+            'company__name',
+            'description',
+            'image_url',
+            'target',
+            'max_count',
+            'active_from',
+            'active_until',
+            'mode',
+            'promo_common',
+            'created_at',
+    )
+
     def get_queryset(self):
         return super().get_queryset()
 
     def with_related(self):
         return (
-            self.select_related('company')
-            .prefetch_related('unique_codes')
-            .only(
-                'id',
-                'company',
-                'description',
-                'image_url',
-                'target',
-                'max_count',
-                'active_from',
-                'active_until',
-                'mode',
-                'promo_common',
-                'created_at',
-                'company__id',
-                'company__name',
-            )
+        self.select_related('company')
+        .prefetch_related('unique_codes')
+        .only(
+            *self.with_related_fields,
         )
+    )
 
     def for_company(self, user):
         return self.with_related().filter(company=user)

promo_code/business/serializers.py

@@ -271,13 +271,12 @@ def get_promo_unique(self, obj):
     def update(self, instance, validated_data):
         target_data = validated_data.pop('target', None)
 
-        for attr, value in validated_data.items():
-            setattr(instance, attr, value)
+        instance = super().update(instance, validated_data)
 
         if target_data is not None:
             instance.target = target_data
+            instance.save(update_fields=['target'])
 
-        instance.save()
         return instance
 
 

promo_code/business/views.py

@@ -74,28 +74,21 @@ class CompanyPromoListCreateView(rest_framework.generics.ListCreateAPIView):
         rest_framework.permissions.IsAuthenticated,
         business.permissions.IsCompanyUser,
     ]
-    # Pagination is only needed for GET (listing)
     pagination_class = core.pagination.CustomLimitOffsetPagination
 
-    _validated_query_params = {}
-
     def get_serializer_class(self):
         if self.request.method == 'POST':
             return business.serializers.PromoCreateSerializer
 
         return business.serializers.PromoReadOnlySerializer
 
-    def list(self, request, *args, **kwargs):
+    def get_queryset(self):
         query_serializer = business.serializers.PromoListQuerySerializer(
-            data=request.query_params,
+            data=self.request.query_params,
         )
         query_serializer.is_valid(raise_exception=True)
-        self._validated_query_params = query_serializer.validated_data
+        params = query_serializer.validated_data
 
-        return super().list(request, *args, **kwargs)
-
-    def get_queryset(self):
-        params = self._validated_query_params
         countries = [c.upper() for c in params.get('countries', [])]
         sort_by = params.get('sort_by')