"post_complete_transaction" event

[XFFA.IR Bot]

Since 2.1.6, there is a postCompleteTransaction method in XF\Purchasable\AbstractPurchasable. However, there may be a need to watch all completed transactions for all Purchasables, for example for sending fiscal receipts to the tax service (not from a payment provider). Extending a class for each Purchasable is inconvenient, since it is impossible to handle for every possible case, so an event like post_complete_transaction would be nice.