node_memory_MemAvailable_bytes is a better estimator than the sum I used before
says some Prometheus documentation.  It is also almost the same, but reads nicer.

nixpkgs update 2022-05-23

See merge request !301

Borgbackup

Closes privatestorageops#314

See merge request !297

Reword SSH private key for CD docs

See merge request !296

Grafana Resources Dashboard: Add user cipher text panel

See merge request !295

Avoid an nginx timeout on the redemption endpoint

See merge request !299

This reverts commit c8a13555.

Sadly, Borg says this is not a good idea: https://borgbackup.readthedocs.io/en/stable/faq.html#can-i-backup-from-multiple-servers-into-a-single-repository

Spoiler:  This won't work, Borg does not guarantee consistency with
parallel writers to the same repo as I now found out.

It's not really a key, and not really public, but not secret either.
This way, the tests can run.

weekly nixpkgs update (2022-04-25)

See merge request !294

Log retention policy module

See merge request !290

Add flo to prod: ssh key + root access

See merge request !292

Add flo's ssh key to the staging grid root user authorized_keys

See merge request !291

Configure journald to discard logs before they're older than 30 days

Closes privatestorageops#221

See merge request !285

This is only semi correct. We keep logs up to what's specified in the privacy
policy.  Currently, that is implemented as keeping them for up to 30 days on
the individual nodes as well as on the central Loki server.