Swagger spec fails `openapi-generator validate`

[NathanHowell]

The Swagger spec fails validation, as well as generation. There are a handful of simple issues:

• The spec is a .json file but is not valid json: some strings are not quoted. It is however valid yaml.
• There are many duplicate response codes, e.g. 400 (Bad UUID) 400 (Bad JSON) 400 (Bad Subtype). Swagger and OpenAPI 3.0 only use the status code 400 with the addition of a oneOf schema to support multiple response types.
• patternProperties and $schema are not supported - see https://swagger.io/docs/specification/data-models/keywords/