The following configuration generates a systemd unit that doesn't
start.
```nix
{
services.syncthing = {
enable = true;
user = "my-user";
};
}
```
It fails with
```
systemd[1]: Started Syncthing service.
systemd[6745]: syncthing.service: Failed to determine group credentials: No such process
systemd[6745]: syncthing.service: Failed at step GROUP spawning /nix/store/n1ydz3i08nqp1ajc50ycy1zribmphqc9-syncthing-1.1.4-bin/bin/syncthing: No such process
systemd[1]: syncthing.service: Main process exited, code=exited, status=216/GROUP
systemd[1]: syncthing.service: Failed with result 'exit-code'.
```
This is due to the fact that `syncthing` group (default) is not
created if the user is overridden.
Add a separate check for setting up the default group, so that
user/group are created independently.
Upstream switched to a different type of ipset table, whereas we
create ipset in post-start which overrides upstream, and renders
sshguard ineffective.
Remove ipset creation from post-start, and let it get automatically
by upstream script (sshg-fw-ipset) as part of startup
Introduces a trim timer similar to the fstrim service.
According to zpool(8) for consumer hardware periodic manual TRIM
is preferred over automatic TRIM that ZFS implements.
The period of one week is based on recommendations of fstrim.
Regression I caused with 3944aa051c, sorry
for this! The Nextcloud installer broke back then because
`trusted_domains` was an empty value by default (a.k.a an empty array)
which seemed to break the config merger of Nextcloud as Nextcloud
doesn't do recursive merging and now no domain was trusted because of
that, hence Nextcloud was unreachable for the `curl` call.
One of the main problems of the Nextcloud module is that it's currently
not possible to alter e.g. database configuration after the initial
setup as it's written by their imperative installer to a file.
After some research[1] it turned out that it's possible to override all values
with an additional config file. The documentation has been
slightly updated to remain up-to-date, but the warnings should
remain there as the imperative configuration is still used and may cause
unwanted side-effects.
Also simplified the postgresql test which uses `ensure{Databases,Users}` to
configure the database.
Fixes#49783
[1] https://github.com/NixOS/nixpkgs/issues/49783#issuecomment-483063922
