Add CRUD API endpoints for native comments

The native comments are in their current form (5.30.0) very nice and convenient, but they lack somewhat when it comes to API mgmt.

Would be useful if it was possible to create new comments, including setting of creator, created date etc, via the API.

Seems it’s currently possible to create comments via the API, but not update a comment’s associated member, when it was created etc.
This makes migration of comments from other blogging tools difficult or impossible (at least when it comes to migrating to ghost Pro).

Suggestion: Implement a full set of CRUD endpoints for native comments, making it possible to update all comment related fields.