Subclassing JSONSchema validator class with OAS30Validator

[p1c2u]

OAS 3.0 is incompatible with JSON Schema because it assumes context-sensitive validation (readOnly and writeOnly for request and response), which JSON Schema doesn't support.

Subclassing jsonschema validator classes is not intended to be part of their public API but it's the only way to add context-sensitive validation support.

[p1c2u]

With new OAS30ReadValidator and OAS30WriteValidator this is no longer the case hence closing.