[bug#69513] Adding a couple new features and tests

[Richard Sent <richard@freakingpenguin.com>]

Hi all,

> Please consider adding a system test for this: as previously
> discussed, we try hard to have tests for every system service.

I have a few changes I plan on submitting soon regarding the restic
service. FYSA Giacomo, I'm writing system tests as well, although those
tests will obviously be limited to local repositories.

For the curious I'm working on the following changes:

1. Add an init? field to attempt to bootstrap local repository
initialization, ala https://github.com/NixOS/nixpkgs/pull/307962

2. Add support for Restic's password command feature in addition to the
existing password file

3. Either add rclone to the profile or add an extra-packages field to
restic-backup-job so restic-required packages can be located in one
spot.

4. The aforementioned tests

I haven't used restic before so this might be harder than I think it'll
be. So far things seem to be going well.

-- 
Take it easy,
Richard Sent
Making my computer weirder one commit at a time.