PRs ready for review _

I’ve done a number of refactorings to the systemd module that are convenient to have for further work that is being done on placing systemd in initrd. I have a number of changes ready that I’d like to submit as a separate PR, but I think the refactorings have value on their own and are easier to review.

Let me know what you think:

https://github.com/NixOS/nixpkgs/pull/164016