Create automation to curate users

[akatsoulas]

We should create either a celery task or a k8s task that will utilize the deletion pipeline to curate users regularly

[smithellis]

Since we will have purged no-content, non-fxa/ma migrated users already, I propose we look for users who haven't logged in in three years, then put them through the new deletion pipeline. We can do this weekly.

[smithellis]

My proposal is here: mozilla/kitsune#6590

It uses the user deletion pipeline, a management command and (for now) cron. I've left it as WIP because we may prefer a different approach - doesn't need to get merged unless we agree on the methodology.

[smithellis]

mozilla/kitsune#6590

[emilghittasv]

Testing activities are blocked for this ticket until the #2161 work lands & is tested in stage.

Deleting users who haven't logged in for more than 3 years will also trigger the deletion of those accounts which were not fxa-migrated. So in order to successfully test #2161, we need to pause the testing activities for this ticket.

The work for this ticket is under a waffle flag/currently disabled.