Managing servers remotely is a big usecase, and deploy-rs is a flake
first deployment tool. By default, all nixosConfigurations are also
setup as deploy-rs nodes.
You'll still need to do some manual ssh setup, but other than that, the
system is ready to deploy.
* Move extern lists to their own folder
* Move unstable package and module imports to their own folder
* Create a genPkgs function to avoid using legacyPackages for the whole
package set
* Move hmActivationPackages to legacyPackages
* fix nixos-option
* use flake-compat for all backward compat concerns
* rebuild devshell after any nix file changes
* reexport system pkgs as legacyPackages
* provide lib flake output
* provide flake lib to nixos configs via `lib.flk`
* clean up flake.nix
