edx/edx-platform — pull request #1744 by flowerhack (2013-11-21 22:25:20+00:00)
Title: Events for entering verified flow & buying

So, the info about whether or not any given order is actually an "upgrade" was only passed through the pre-purchase GET url before. Hence, my attaching an "upgrade" field to Order, so that can get passed through for event-triggering purposes once the certificate is actually purchased.