discount codes from license keys

Since the NSFW takedown from gumroad, a lot of users have switched to selling on jinxxy. People who have previously purchased stuff on gumroad should be able to access the product on jinxxy using the license key as a discount code. This means dynamic discount codes that the user can set up by attaching a product link from another website.

tl:dr: Any purchase of a product from the another website (gumroad) will generate a [number]% off discount code that can be used on jinxxy.