JSON:API 1.1: Add descibeBy API to add link to top level, resource and relationship objects

Problem/Motivation

describedby: a link to a description document (e.g. OpenAPI or JSON Schema) for the link target.

The describeBy attribute is a link to something like a OpenAPI or JSON schema (or similar) description of the element. This attribute can appear on any of the following levels:

A link’s context is the top-level object, resource object, or relationship object in which it appears.

So it could appear in the links object of the following objects:

/jsonapi/node/article (top level object)
/jsonapi/node/article/[id] (resource objects)
/jsonapi/node/article/[id]/author (relationship objects)

This could be implemented as events, which is relatively easy. But i have a feeling this might not be the optimal way.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet