When there are changes in the shipping address in the checkout, a callback is sent to
session.express.shipping_address_callback with the new address.
The webshop should update the webshop state/order with the new shipping address, and (if
shipping in iframe is
enabled) return the new list of available shipping options.
Look here for the documentation of the callback.
If the checkout is embedded, the Dintero Web SDK will call
onSession whenever the session is updated, with the