done: integrate with payment

core/apps/payment/serializers.py

@@ -1,8 +1,13 @@
 from rest_framework import serializers
 
+from core.apps.orders.models import Order
+
 
 class PaymentSerializer(serializers.Serializer):
     order_number = serializers.IntegerField()
     price = serializers.IntegerField()
 
-    
+    def validate_order_number(self, value):
+        if not Order.objects.filter(order_number=value).exists():
+            raise serializers.ValidationError("Order not found")
+        return value