add: order model, order create api, order create serializer, order item model

core/apps/orders/serializers/order.py

@@ -0,0 +1,45 @@
+from django.db import transaction
+
+from rest_framework import serializers
+
+from core.apps.orders.models import Order, OrderItem
+from core.apps.products.models import Product
+
+
+class OrderItemCreateSerializer(serializers.Serializer):
+    product_id = serializers.UUIDField()
+    quantity = serializers.IntegerField()
+
+    def validate(self, data):
+        product = Product.objects.filter(id=data['product_id']).first()
+        if not product:
+            raise serializers.ValidationError("Product not found")
+        data['product'] = product
+        data['price'] = product.price * data['quantity']
+        return data
+    
+
+class OrderCreateSerializer(serializers.Serializer):
+    items = OrderItemCreateSerializer(many=True)
+    
+    def create(self, validated_data):
+        with transaction.atomic():
+            order_items = validated_data.pop('items')
+            order = Order.objects.create(
+                user=self.context.get('user'),
+            )
+            items = []
+            total_price = 0
+            for item in order_items:
+                items.append(OrderItem(
+                    product=item.get('product'),
+                    price=item.get('price'),
+                    quantity=item.get('quantity'),
+                    order=order,
+                ))
+                total_price += item.get('price')
+            OrderItem.objects.bulk_create(items)
+            order.total_price = total_price
+            order.save()
+            return order
+