create a resource for backups

Originally created by @groente on #16202 (Redmine)

we want lizard to push backups of its logical volumes to stone. this calls for a puppet resource to take care of the initialisation of a backup repository and weekly pushes to said repo.

Feature Branch: puppet-tails:feature/16202-create-resource-for-backups

Parent Task: #15071 (closed)

Edited May 15, 2020 by groente

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information