Discussion/FR: OAS validation

[glickbot]

Some APIs may have non-valid OAS keys, and while it's probably not the goal of gnoistic to "make a client for every API", it might be worth discussing if we want to handle/error on APIs that aren't OAS compliant. As an example, the Google Discovery v1 API refers to the '$ref' as the key name, but '$' may not be OAS compliant (non-ASCII letter key).

Related conversation: https://github.com/googleapis/gnostic-go-generator/issues/9

[timburks]

I think at-least-optional full OpenAPI 3 validation would be great to have. I would say that Discovery support is less important than rich OAS support.