[Feature] Schema from OpenAPI

[bradjones1]

Follow-up from #706 (comment).

It would ease adoption of Orbit if we could support auto-generation of Orbit schema from common formats, e.g. OpenAPI.

I come from Drupal-land and there is OpenAPI support for json:api (and probably GraphQL?) already. Currently a helper module like https://github.com/bradjones1/orbit-schema-from-openapi is required to translate schemas from OpenAPI to Orbit's bespoke format.