Make sure to send an idempotency key to Stripe
Make sure to send an idempotency key to Stripe

The article had previously suggested that an idempotency key was being
sent, but I'd forgotten to actually do so. Here we add that in with a
comment.


Former-commit-id: d9037734324c0d17a357996a937d952ad9c14358
brandur/sorg,brandur/sorg,brandur/sorg,brandur/sorg,brandur/sorg