Auto-update attendance frequency

[dehnert]

Gate is split up by attendance frequency -- "every", "monthly", "rarely", "never" -- which limits scrolling in the common case of frequent attendees showing up. We should automatically update this.

I think my theory was to do something like "count how many times somebody has showed up in the last month and the last year", and then:

• If they've come in the last month, put them in every or monthly
• If it's at least like 20 times in the last year, every
• If it's at least four times, monthly
• If it's ever, rarely

(Maybe we look at the entire SquaresDB attendance history for rarely vs never, not just the year.)

I think this should be a batch process. I'm not sure whether it should be weekly or like monthly. I guess weekly seems fine?

[manya-t]

Gonna look at this one

[dehnert]

My thinking was to do this as roughly a cronjob -- presumably write a Django management command, and then somebody should update Ansible to add a crontab line or a systemd timer unit or something.

We should make sure to integrate this with reversion (the Django DB version control library we use). Presumably all the frequency updates in one run should be one reversion ~transaction.