Recent changes merged in #10877 didn't handle these events
correctly. The linkified_id function breaks for the `discount`
object in the JSON payload. A cursory glance at Stripe's docs
tells me that since a discount is associated with a customer
or a coupon, it makes sense for a `discount` object to not have
an ID that can necessarily be linked to. So, we can just link
to the associated coupon instead.
Eeshan Garg