Make the reversal payment feature extensible
The current reversal payments actions aren't extensible. There isn't any way to hook in the behavior when a payment is reversed.
The fast and quick fix would be to make the `addTransaction` and `addInvoicePayment` hooks behave like they should be (when a transaction is added, all transactions).
A more useful and nicer fix would be to able to add custom actions, toggle-able through the Setup => Automation window, just like the current 2 actions defined (set invoice status and revert product due dates).