Update openapi spec to 2021-10-05

[imalsogreg]

Hello! I've tried bumping the spec3.json file to the most recent one provided by Stripe.

Following your codegen instructions, there were surprisingly few issues. I did run into a few things however, especially in some apparently new fields that the Stripe API lists as type hash. I've marked these areas with TODO's in the PR. There are about a dozen of them.

I'm posting the PR early, as a draft, in case it's obvious to the maintainers how I should fix this. If you already have your own process for bumping the spec, please feel free to ignore me :) If not, and a bump would be useful, I'd love to help polish this up.

For us, the need for a bump the spec was driven by our use of Stripe subscriptions. The CreateSubscriptionItems schema has changed to accept a Price rather than a Plan, and that's the API we would like to program against.

[arlyon]

I believe there are some new APIs that the codegen doesn't handle very gracefully at the moment, as certain structs are ignored / forgotten in the output. I've been meaning to get round to it but haven't had the free time yet. Happy to provide as much help as you need!