Improve repository check failure alerting
Currently failures of the automatic repository checks on a GitLab server trigger a daily email to all GitLab admins for that server. These alerts repeat every day. The alerting rule is very simple: count the number of projects in the SQL database that have the 'last check failed' flag set to true. If the number is greater than zero, email all GitLab admins.
The only way to silence the alerts is to:
- fix all the repository problems OR
- disable the check feature and clear all check states (from the admin settings page)
I am not sure if this is optimal. If the problem, whatever it is, does not get fixed by the next day, admins will start ignoring the alert emails, or turning the feature off. Either way it stops being useful.