Database and API for Git abuse rate limiting alerted users

What does this MR do and why?

This MR adds the database and api part for the alerted users feature for Git abuse rate limiting.

MR's for this feature (in order of dependency):

• Database and API for Git abuse rate limiting al... (!110760 - merged) (current)
• Datahelpers and Throttle Services for Git abuse... (!110762 - merged)
• Frontend for Git abuse rate limiting alerted users (!110759 - merged)

Issue: https://gitlab.com/gitlab-org/modelops/anti-abuse/team-tasks/-/issues/186+

Screenshots or screen recordings

	Admin settings	Group settings
Before
After

How to set up and validate locally

1. Cherry pick all commits from the MR's mentioned in the description (alternatively, checkout the add-alerted-users-to-git-abuse-rate-limiting branch, which has them all)
2. Enable the feature flag

   Feature.enable(:git_abuse_rate_limit_feature_flag)

3. Visit the Git abuse rate limit admin settings: http://localhost:3000/admin/application_settings/reporting
4. Add and/or remove users from Send notifications to field
5. Click Save changes
6. Visit the Git abuse rate limit group settings: http://localhost:3000/groups/${group_name}/-/settings/reporting
7. Add and/or remove users from Send notifications to field
8. Click Save changes

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.