Coupa punchout
Per Coupa's punchout ordering guide, Coupa sends your store a PunchoutSetupRequest with the user's details. Your store logs them in and replies with a landing page URL. At checkout, your store sends a PunchoutOrderMessage, and the items land on the buyer's requisition. After approval, Coupa sends an OrderRequest. The same guide lists the common setup errors, such as a wrong URL, a login failure and no cart returned.
