feat: add Debian packaging

[enneamer]

I have tried to build it with git-buildpackage on Debian Bookworm, and it works. Maybe it needs some linting, but I think we can save it for later.

[gsauthof]

Do you plan to integrate such a package into the debian distribution?

What are the steps to build such a package?

[enneamer]

Thank you for your review, @gsauthof .

Do you plan to integrate such a package into the debian distribution?

Sorry that I did not make my intention clear. In this pull request, I merely add necessary code for Debian packaging. This can help people who wish to build a Debian/Ubuntu package to deploy on their own machines, especially when they have many machines to manage and wish to share a system package for easier deployment. In addition, in case this project is to adopt GitHub Actions to offer pre-built packages in the future, this PR might be helpful. (I am aware that there are solutions to packages for many distros. I am not sure how well they would work for system packages like this, which might need distro-specific modifications.)

What are the steps to build such a package?

I should have included information like this. Do you mind me putting it in README.md in the PR?

[enneamer]

I have added a packaging guide in README.md.

[gsauthof]

Say I'll merge your pull-request - would you be available to help out with issues/pull-request reported on that debian packaging (in case there are any)?

Ideally, having the debian packaging stuff in this repository would be just a temporary solution until a debian packager adds a dracut-sshd package to the official Debian repository.
Then the debian packaging files could be maintained outside of this repository.

FWIW, I packaged some software for debian more than a decade ago but repressed most memories.
Especially the debian way of splitting the packaging specification over a multitude of files annoyed me very much.

For Fedora and other RPM distributions (where dracut-sshd isn't an official package yet) I'm using the COPR service.
Is there something similar for debian?

[enneamer]

I'll be glad to deal with issues and PRs related to Debian packaging. I have added relavant information in debian/README.md.

And I agree that it would be better to have a Debian maintainer to take on the work. Yet I haven't seen a packaging request on bugs.debian.org , so I guess it won't happen very soon.

As for third-party package hosting, Debian itself does not have an official platform similar to COPR to my best knowledge. Ubuntu has PPAs, and many contributors publish their Debian packages there as well. For non-official ones, packagecloud.io provides unified hosting across many distros, including DEB and RPM.

[gsauthof]

Ok, I came to the conclusion that this repository isn't the best place for debian packaging files.

If not already present I would even put the RPM packaging into a separate repository, today.

So the alternatives are:

1. try to get dracut-sshd into the official Debian package repository
2. create a separate github repository for debian packaging

Either way, I'm happy to link any such effort from the README, if something materializes.