Shopify/active_merchant — pull request #260 by stiak (2012-02-01 03:38:04+00:00)
Title: Add support for setting up the Instant Update API callback

While testing this against the paypal sandbox I found that the ordering of elements in the XML was actually pretty important. Without the ordering here the request would fail saying it couldn't find the flat rate shipping options. The order here is the order from the latest XSD's.