The Checkout resource will no longer include the web_processing_url parameter
API
Effective December 04, 2017
On December 4, 2017, we will be removing the web_processing_url parameter from the Checkout resource. The web_processing_url was never documented and never intended to be consumed by Shopify applications. This does not remove any functionality from the API, since the web_url parameter remains and continues to provide the same functionality.