Can it be possible to add the license purchase key in author invoice

hi, can it be possible for evanto to add the license key related to a purchase in our author invoice then we can build better system to verify license and not have to query the api for no reason. example i have created a forum where my buyers can register with their email and purchase key but if someone receive a refund then the only way for me to know it is to revalidate that user key on a regular basis when he login to my system. adding the purchase key in our author invoice can be a great thing since all we can have to do is to mark that refunded key as invalid in our own system and not query evanto api.

ps: or at least if not the key maybe only the evanto username of the buyer can do the job.