post
https://staging.creditkey.com/app/ecomm/complete_checkout
After return from Credit Key, complete_checkout is called to confirm successful placement of an order. If the return value for 'success' is 'true', the order should be placed in the merchant system; otherwise, no order should be placed.
400The order key was not provided.
401Unauthorized. The public_key and/or shared_secret given are invalid.
404An order with the given order key was not found.
