Hotfix 1.10.x sup 15603

[plyhun]

Abstract

REST EPs for referenced projects of (micro)schema.

Checklist

General

• [x] Added abstract that describes the change
• [x] Added changelog entry to /CHANGELOG.adoc
• [x] Ensured that the change is covered by tests
• [x] Ensured that the change is documented in the docs

On API Changes

• [x] Checked if the changes are breaking or not
• [x] Added GraphQL API if applicable
• [x] Added Elasticsearch mapping if applicable

[plyhun]

This is a new feature (new endpoints), so there is no reason to add it as hotfix.

@npomaroli it is declared as SUP though. I may indeed move it under GP (2.1.x), although it will seem to be an unplanned feature.