Add "create promotion code" API

[TmLev]

Summary

This PR enables users of async-stripe to create promotion codes.

I needed to programmatically create a lot of promotion codes, and since I couldn't find a way to achieve this with async-stripe, I've added it manually.

Checklist

• [x] ran cargo make fmt
• [x] using conventional commits to hightlight user-facing fixes and features

[TmLev]

Now that I look at it, I don't feel like this API should be a part of the checkout feature. Where should we put it though?

[augustoccesar]

Now that I look at it, I don't feel like this API should be a part of the checkout feature. Where should we put it though?

Stripe seems to put it under "products". So maybe can be under #[cfg(feature = "products")]?

[TmLev]

So maybe can be under #[cfg(feature = "products")]?

Great idea! Done.

[TmLev]

@arlyon a kind ping – reviewing this shouldn't take longer than two minutes of your time :)

[arlyon]

Running CI

[TmLev]

CI / verify-codegen (pull_request) Failing after 57s

Not sure this particular PR has anything to do with the codegen?.. Please correct me if I'm wrong

[TmLev]

@arlyon is there anything I can do to help you with the pipeline?

[arlyon]

No that task is broken, haven't had a chance to look at it. Merged! New release should pop up soon (and leave a comment here).

[arlyon]

:tada: This PR is included in version 0.39.0 :tada:

The release is available on:

• v0.39.0
• GitHub release

Your semantic-release bot :package::rocket: