tl;dr What information does the IPN send to distinguish the variation, in an eBay multi-variation listing transaction?
I've been using the IPN for about ten years now, for both website and eBay transactions. I want to change some of my listings on eBay to multi-variations though. At the moment I store the eBay item ID in the local database, and use this (passed by the IPN) to construct and store the customer order in the local database. The product SKUs are stored on eBay, but as these are not sent through the IPN I don't/can't use them.
I assume that for multi-variation listings, each variation shares the same eBay item ID. Is that correct? And if so, what information is transmitted through the IPN to distinguish between variations on one item?
I'm sure the solution is pretty simple, but I'm struggling to find documentation for it.