How to directly access the OT2 Markup Service?

This question is in reference to this Viewing Service API Document.

The doc says: "Your integration does not typically have to interact directly with the Markup Service because the viewer's markup API below almost certainly does everything you need."

However, I have a requirement where I want to do "headless" modifications to the markup data for a document. That is, I don't want to open the OT2 Viewer to modify the markup data. For this, I need to interact with the Markup Service directly via REST calls, just like how the rest of the OT2 services are served. How do I do this?

Essentially, I am looking for some services like these:

  1. GET /markup/document-identifier - This should return all the existing markup IDs for a document.
  2. GET /markup/document-identifier/markup-identifier - This should return the markup XML for the given document and markup ID.
  3. POST /markup/document-identifier/markup-identifier - The body of the request should have a markup XML that I want to set for the document.