Expect OK response when unsubscribing from a registry entry

MERGE REQUEST

MR Guidelines

Overview

This MR adds an "OK" response to the unsubscribe flow of the registry subscription. That way the renter knows when to stop expecting notifications for an unsubscribed entry and when to start punishing hosts for wasting bandwidth with unsubscribed entries.

Checklist

Review and complete the checklist to ensure that the MR is complete before assigned to an approver.

• All new methods or updated methods have clear docstrings
• Testing added or updated for new methods
• Any new packages are added to Makefile and .gitlab-ci.yml
• API documentation updated for API updates
• Module README.md updated for changes to workflow
• Issue added to Sia-UI repo for new supporting features
• Changelog File Created

Issues Closed