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.

Fix docs code blocks

See merge request !289

nixpkgs update 2022-04-13

See merge request !287

Add update-nixpkgs / diff-closures documentation

See merge request !288

bump PaymentServer to version exposing more info

Closes privatestorageweb#226

See merge request !284

weekly nixpkgs update (2022-03-28)

See merge request !282

weekly nixpkgs update (2022-03-21)

See merge request !280

```
VirtualBox-GuestAdditions: 6.1.30-5.10.103 → 6.1.30-5.10.106
cpupower: 5.10.103 → 5.10.106
ena: 2.5.0-5.10.103 → 2.5.0-5.10.106
expat: 2.4.4 → 2.4.7
getent-glibc: 2.33-117 → 2.33-123
glibc: 2.33-117 → 2.33-123
glibc-locales: 2.33-117 → 2.33-123
initrd-linux: 5.10.103 → 5.10.106, +75.7 KiB
linux: 5.10.103, 5.10.103-modules → 5.10.106, 5.10.106-modules
locale-glibc: 2.33-117 → 2.33-123
nixos-system-monitoring: 21.11.336340.2ebb6c1e5ae → 21.11.336589.2c66a7a6e03
nixos-system-payments: 21.11.336340.2ebb6c1e5ae → 21.11.336589.2c66a7a6e03
nixos-system-storage001: 21.11.336340.2ebb6c1e5ae → 21.11.336589.2c66a7a6e03
nixos-system-storage002: 21.11.336340.2ebb6c1e5ae → 21.11.336589.2c66a7a6e03
nixos-system-storage003: 21.11.336340.2ebb6c1e5ae → 21.11.336589.2c66a7a6e03
nixos-system-storage004: 21.11.336340.2ebb6c1e5ae → 21.11.336589.2c66a7a6e03
nixos-system-storage005: 21.11.336340.2ebb6c1e5ae → 21.11.336589.2c66a7a6e03
nixos-system-storage1: 21.11.336340.2ebb6c1e5ae → 21.11.336589.2c66a7a6e03
nixos-system-storage2: 21.11.336340.2ebb6c1e5ae → 21.11.336589.2c66a7a6e03
openssl: 1.1.1m → 1.1.1n
stage: -19.4 KiB
udhcp: ∅ → ε
util-linux: 2.37.3 → 2.37.4
zfs-kernel: 2.1.2-5.10.103 → 2.1.3-5.10.106
zfs-user: 2.1.2 → 2.1.3, +14.0 KiB

```

Fix RAID alert going off with zero degraded arrays

See merge request !279

This should fix the current alerts for our RAID arrays.
It's only "should" because I can't test it proper without said
RAID arrays in the dev or staging machines.

bump PaymentServer

See merge request !276

bump nixpkgs, esp. for linux 5.10.103

See merge request !277

Factoring improvements (VPN client, monitoring exporters)

See merge request !271

Grafana: Payment dashboard: Revert "Redemption" back to old-style Graph panel

See merge request !270

nixpkgs update 2022-02-28

See merge request !275