//! Implementation of OpenAPI v3.0.X Specification
//!
//! Full specification can be found [here](https://spec.openapis.org/oas/v3.0.4).
//!
//! # Intentional permissive deviations
//!
//! * `PathItem` accepts arbitrary HTTP method names (e.g. `search`, `trace`)
//! in addition to the closed `get/put/post/delete/options/head/patch/trace`
//! set defined in the spec.
//! * `Schema` accepts a `null` type via `NullSchema`. OAS 3.0 has no `null`
//! type (the recommended idiom is `nullable: true` on a typed schema; `null`
//! was added as a real type in 3.1). Kept on purpose so v3.0 specs that
//! borrowed the 2020-12 idiom round-trip cleanly.
pub