Repository mirroring should notify when failed

Description

When repository mirroring fails you only see it if you go to the mirroring page. This is less than ideal because it is basically a silent fail. We are encountering this more often than not where package builds fail because of an un-synced repository .

Proposal

Think of a notification system that would notify on failure. It can be an email to the masters/owners of the repository, a flash message or anything else. As long as someone gets their attention drawn to the fact the mirroring failed.

Added feature proposal label

cc @regisF

@marin For the notification mechanism, do we have already a feature that causes to send an email to an administrator if something happens?

@regisF We have email notification for admins when repositories fail fsck.

Milestone changed to %Backlog

@marin thanks.

We should probably do this after we do this: https://gitlab.com/gitlab-org/gitlab-ee/issues/98

@regisF ping. We have been hit ourselves by mirroring silently failing multiple times now. We really need this four our internal processes.

@marin

what about something like this, to display on the project homepage?

I am not against it if it is shown to team members only. At the moment, I am desperate for any type of notification that will reach multiple set of eyes.

mentioned in issue gitlab-com/infrastructure#910

EE customer requesting this: https://gitlab.zendesk.com/agent/tickets/73038.

added customer label

added SP2 label

https://gitlab.zendesk.com/agent/tickets/78631

Support Ticket: https://gitlab.zendesk.com/agent/tickets/80246

From @abuango's ticket:

it would be very helpful if a message was sent to the admins (or project members) when mirroring stops working for any reason.

I think most customers want some sort of message notification, not just a flash message.