Somewhere between v2.7.0.0 and v2.17.0.0 a lot of things have been made internal in EPiServer.ContentApi.Commerce, e.g. the ProductContentApiModel. This means you cannot extend it in a model mapper. You could use the ContentApiModel, but then you lose the assets, so that's not really an option.
Somewhere between v2.7.0.0 and v2.17.0.0 a lot of things have been made internal in EPiServer.ContentApi.Commerce, e.g. the ProductContentApiModel. This means you cannot extend it in a model mapper. You could use the ContentApiModel, but then you lose the assets, so that's not really an option.