Implement canary checks for all identified security issues

Creating this issue in the Security project while a better project to house this is identified.

As an action item from the Events API issue (gitlab-com/gl-infra/production#477 (closed)), we need to start working on implementing a canary system for all security issues that are patched on GitLab.com. This is required in order to ensure that if regressions takes place, Security is notified of them ASAP.

As part of developing a fix, a canary check for the fix needs to be developed as well. This canary check needs to be run on at least a hourly cadence, and needs to fail every time. In the event that the canary check doesn't fail (i.e. the response contains data that it should not), then an alarm is raised and Security get notified.