admin: config history

[mastercactapus]

Split from #2554

What problem would you like to solve? Please describe:
As an admin, config mistakes happen, or temporary changes need to be made, and it can get difficult to keep track of changes over time.

Describe the solution you'd like:
The ability to review and revert-to old versions of global config.

Listing old versions, with timestamps (as well as diffs) and the ability to easily apply an old version.

A +1 would include the name of the user who updated the config (if applicable) and prompting for a summary/description of changes.

Describe alternatives you've considered:
There are no in-app options.

Additional context:
GoAlert already keeps a full history of config changes in the DB; it is not exposed via GraphQL or the UI to be managed.

[stale]

This issue has been automatically marked as stale because it has not had recent activity.

[mastercactapus]

Closing in favor of general audit log