See https://swagger.io/specification/#media-type-object

...which must have 'in' and 'name' keys

This allows backwards compatible changes in the future.

The `X-` prefix is deprecated as of https://datatracker.ietf.org/doc/html/rfc6648

Currently callback expressions don't allow referencing other operations

So we have to include it separately. It's a little more text.

See https://github.com/OAI/OpenAPI-Specification/issues/417

Closes #81

* The "old" Destination is now in destination-any but still called Destination.
* There is now a PublicDestination (w/o contactInfo and callback) and a PrivateDestination
* Removed notice about missing fields depending on scope (since its now obvious from the schema)