Fix OpenAPI schema

[pjungkamp]

I've noticed several smaller issues with our doc/openapi schema.

1. We were using OpenAPI 3.0.3, which isn't fully JSON Schema draft v7 compatible. I've updated our schema to 3.1.0.
2. The doc/package.json and doc/package-lock.json bit-rotted away. I did some basic maintenance.
3. We didn't even try to test/lint our schema in CI. I've added a redocly lint call to our build:openapi CI and fixed or suppressed all errors to make it pass.

---

Open Questions

• I've disabled the security-defined redocly lint... we don't have any security on our API...
• I've also disabled the lint flagging the servers list in doc/openapi/openapi.yaml for using localhost. Is that list still correct? I can't access the k8s endpoint from the open internet... is there a public endpoint?
• Should we update and maintain the doc/package.json, or remove it entirely? It is useful for local development on the schema.
• Should the doc/package-lock.json really be committed into our repository?

[stv0g]

Great :) Thanks a lot!