Add `prune` command to automatically remove backups older than a given time period

[lbeckman314]

Tip

Feature request from PR #3

• 2. Added culling command + config

https://github.com/ohsu-comp-bio/helm-charts/blob/main/charts/backups/templates/cronjob.yaml It was talked about that there is some method of culling older backups, and keeping around weekly versions once backups are 3+ months older. This way of passively doing backups will be very space inefficient as more and more data enters into the dbs.

Commit TODO ⚠️