Registry subscription tweaks

MERGE REQUEST

MR Guidelines

Overview

This MR adds the public key to the notification response to avoid having to brute force signatures by verifying them with all pubkeys to figure out if the host sent an update we are actually interested in.

It also adds a waitgroup to the subscription info to be better about flushing existing, ongoing notifications and changes the protocol to respond with an "OK" upon unsubscribing from multiple values. This gives the renter certainty that after receiving the "OK", no more notifications for unsubscribed values should arrive.

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