Another possible more simple approach here could be to append the new atrributes to the api helper method class helper like:

```ruby
Spree::Api::ApiHelpers.order_attributes.push :currency, :tax_total, :visit_id, :visitor_id, :pageview_id, :last_pageview_id
```
We could drop this decorator / class_eval here and just add that code somewhere else in this extension.