Create and manage systemd-sysexts.
Due to an upstream bug, we cannot ship nix-based sysexts with SELinux support, and this is bound to break fedora systems, since they require SELinux labels on /usr and it's subdirectories.
If you want to try out this project now, please either try it out on a VM, or disable SELinux (permanently, because sysexts persist cross-reboot) on your host.