As I still maintain the demo instance, it's useful to integrate the demo
instance into the current terraform configuration, this allows it to
benefit from further developement of this repository.

The current README and variable descriptions should help anyone
interested in creating their own demo instance equivalent, to deploy
this to their hetzer cloud account. Even if not, it might provide some
nice inspiration regarding the instance handling.

This patch drops the unused subnet variable from the hcloud_instance
module, which wasn't used anyway. This help to make the module fully
compatible with the way the hedgedoc demo instance is deployed.

Since the secrets path is only available inside the container, but the
systemd-run command is executed outside the container, it can't access
the secret path, therefore the file needs to be copied.

This patch fixes issues currently faced by longhorn, where the SELinux
policy denies a DAC_override for iscsid. Since I couldn't find on what
file it even tries to do this override, for now, this override to fix
unmountable volumes.

There have been multiple indicators, that the postfix TLS settings are
not ideal therefore this patch aims to imprive the situation.

Reference:
https://ssl-config.mozilla.org/#server=postfix&version=3.4.8&config=intermediate&openssl=3.0.8&guideline=5.6

I currently don't really use loki while it causes some trouble due to S3
problems. Therefore this patch drops loki again.

Currently the authentication skipping doesn't work as expected, given
the goal is a public facing status page, for now the uptime-kuma
internal auth will have to do, it'll be replaced soon.