Don't schedule jobs that are owned by ex employees and send alert about it to find new owner

[ThomasMoz]

Once folks have had their ldap revoked, we should not be running orphaned jobs.

[fbertsch]

Related bug for updating emails of non-participants: https://bugzilla.mozilla.org/show_bug.cgi?id=1452955

Related issue for this data in mozilla-iam: https://github.com/mozilla-iam/iam-project-backlog/issues/238

[mreid-moz]

Note that we shouldn't delete these jobs, we should simply stop scheduling them and send an alert. They may still be needed, but their ownership reassigned.

[ThomasMoz]

Mark's description is far more succinct than mine - Do what he says :)

[jezdez]

@mreid-moz Send an alert where exactly? Should the alert be sent every time the job would have been scheduled?

[jezdez]

I've updated the issue title accordingly

[mreid-moz]

I think sending it to telemetry-alerts would suffice. A one-time alert when the job is unscheduled is ideal.

[jezdez]

Would it suffice as a workflow for someone with admin permissions to go to the Django admin to do this "unscheduling"?

There is some reliance to fix #196 first by the way.