I've seen this time and time again in IRC, and in the forums. Users want to have side effects from buying something in the Shop. Often times, it's just adding a user to group, but the Subscription Asset isn't flexible enough for that (it doesn't have inventory, or variants, or whatever).
We should add a workflow to the Sku class. The default would be no workflow. However, users could build custom workflow to do whatever they need to have done.
Possible immediate uses:
