rancher check unique - pos free products check unique - 500 error handling

apps/herd/pos/api/v1/serializers.py

@@ -42,6 +42,8 @@ class RancherSerializer(serializers.ModelSerializer):
         if self.Meta.model.objects.filter(national_code=attrs['national_code']).exists():
             raise UniqueRancherApiException()
 
+        return attrs
+
     def to_representation(self, instance):
         """ customize output of serializer """