v4 API: Subscribers

[n7studios]

Summary

Adds support for endpoints in the subscribers section of the v4 API.

Testing

Tests pass.

Checklist

• I have written a test and included it in this PR
• I have run all tests and they pass
• The code passes when running the PHP CodeSniffer
• The code passes when running PHPStan
• I have assigned a reviewer or two to review this PR (if you're not sure who to assign, we can do this step for you)

[noelherrick]

Looks good. As far as the lines that cleanup the subscribers (by unsubscribing them), is there a way to put that into a method or block that always runs, even if there's an assertion failure?

[n7studios]

Looks good. As far as the lines that cleanup the subscribers (by unsubscribing them), is there a way to put that into a method or block that always runs, even if there's an assertion failure?

Yes - I'll open a PR for that today.