v0.6.0

Second pre-release. This adds support for a few more conversions:

Convert type arrays to nullable

If a schema has a type array of exactly two values, and one of them
is the string 'null', the type is converted to the non-null string item,
and nullable: true added to the schema.

For example:

    myResponse:
      title: My Response
      description: Response from an API operation
      type: [ object, 'null' ]
      allOf:
        ...

becomes

    myResponse:
      title: My Response
      description: Response from an API operation
      type: object
      nullable: true
      allOf:
        ...

and

    myResponse:
      title: My Response
      description: Response from an API operation
      type: arrray
      items:
        type: [ 'string', 'null' ]
        ...

becomes

    myResponse:
      title: My Response
      description: Response from an API operation
      type: arrray
      items:
        type: string
        nullable: true
        ...

This transformation does not handle more complex type array
scenarios such as

   type: [ number, string, boolean, 'null']

To support that, the schema would need to be recast using oneOf,
but this is not trivial do to other schema attributes that may
be possible (properties, allOf etc.)

(Contributions welcome.)

Remove unevaluatedProperties

The tool removes the unevaluatedProperties value, introduced in later
versions of JSON Schema,
as this is not supported in OAS 3.0 JSON Schema Draft 7
used in OAS 3.0.

    myResponse:
      title: My Response
      description: Response from an API operation
      type: object
      unevaluatedProperties: false
      allOf:
        ...

becomes

    myResponse:
      title: My Response
      description: Response from an API operation
      type: object
      unevaluatedProperties: false
      allOf:
        ...

Remove schema $id and $schema

The tool removes any $id or $schema keywords that may appear
inside schema objects.