btrfs: missing btrfsmaintenance configuration

It's not recommended to mount with discard (continuous trim mount option), but instead systems need to run periodic trim and scrub jobs.

Debian has the package btrfsmaintenance for this (https://salsa.debian.org/sten/btrfsmaintenance).

Btrfs maintainance (scrub), monitoring the rootfs as well as external disks (smartd?), and sending emails to the Freedombox admin on problems, would seem quite necessary to actually bring practical data-safety to the users.

A configuration value discussion: https://www.reddit.com/r/btrfs/comments/hc2nlu/maintaining_my_btrfs_partitions/