Provide a mechanism for automatically updating the OpenAPI spec

[goshatch]

Some automation that would pull the latest JSON into our repository.

Ref: https://github.com/bluesky-social/bsky-docs/tree/main/atproto-openapi-types

[goshatch]

The solution I'm imagining here is some kind of script outside of the main code base, that would compare the latest spec provided by the Bluesky team with the version we're vendoring, and somehow update it in our own repository.

This could run either locally on a developer's machine, or as part of a CI pipeline (in GitHub Actions for example).

It would need to somehow guard against unexpected changes in the official spec breaking compatibility. This could be done by running some unit tests against the updated spec, or by automatically creating a PR with the changes and letting someone review them.