Generate OpenAPI definitions automatically from Go code

[jsoriano]

There is an openAPI definition available in the repository, but there is nothing checking that it is maintained up to date with the actual implementation.

Consider strategies to maintain this definition updated.

[mtojek]

QQ: Do we know if anyone uses the OpenAPI posted in the package-registry? If we know that it's outdated/incorrect/not usable, maybe it's better to remove it and:

1. Leave another issue to support any kind of generation.
2. Forget about it.

[jsoriano]

+1 to remove it by now if not used (or not usable).

I would keep an open issue about providing an OpenAPI definition or something similar. I think this would be a nice to have, and can be also helpful for us to generate documentation.

[jsoriano]

FTR, it seems there was a discussion about using registry's open API in Kibana/Fleet, but it was discarded: elastic/kibana#70711