add MS for .subscriber.reference to RelatedPerson

[f-peverali]

Contributor Pull Request

Description

Solves Anfisk 244

Motivation and Context

How has this been tested?

Snippets or Screenshots (if necessary):

Types of changes

• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this IG / specification.
• My change requires a change to the documentation or narrative (intend) of the IG.
• I have already updated the documentation / narrative (intend) accordingly.
• ReleaseNotes for feature/fix are updated in releaseNotes.md