Re-structure flake

[brianmcgee]

• introduces flake.parts for a modular approach to composing the flake outputs
• configures treefmt for nix fmt which enables the following:
  • alejandra to format .nix files
  • deadnix to remove dead nix code
  • statix to avoid nix anti-patterns
  • shellcheck to lint shell scripts
  • mixes in a flake check
• exposes user, service and host NixOS modules in the nixosModules flake output
• uses self references to the aforementioned NixOS modules when composing NixOS configurations
• adds reuse-lint to check for copyright header issues when running nix flake check
• adds flake-compat to ensure non-flake users can work with the repo and moves the devshell definition into the flake devShells.default output
• adds a .envrc file for direnv users to automatically drop into the default dev shell when cd'ing into the repo

❯ nix flake show
git+file:///home/brian/Development/github.com/tiiuae/ghaf-infra?ref=refs%2fheads%2ffeat%2fre-structure-flake&rev=60b187f064847e65a0471fe4ced9c4fcec8337f5
├───apps
│   ├───aarch64-darwin
│   ├───aarch64-linux
│   ├───x86_64-darwin
│   └───x86_64-linux
├───checks
│   ├───aarch64-darwin
│   │   ├───reuse: derivation 'reuse-lint'
│   │   └───treefmt: derivation 'treefmt-check'
│   ├───aarch64-linux
│   │   ├───reuse: derivation 'reuse-lint'
│   │   └───treefmt: derivation 'treefmt-check'
│   ├───x86_64-darwin
│   │   ├───reuse: derivation 'reuse-lint'
│   │   └───treefmt: derivation 'treefmt-check'
│   └───x86_64-linux
│       ├───reuse: derivation 'reuse-lint'
│       └───treefmt: derivation 'treefmt-check'
├───devShells
│   ├───aarch64-darwin
│   │   └───default: development environment 'nix-shell'
│   ├───aarch64-linux
│   │   └───default: development environment 'nix-shell'
│   ├───x86_64-darwin
│   │   └───default: development environment 'nix-shell'
│   └───x86_64-linux
│       └───default: development environment 'nix-shell'
├───formatter
│   ├───aarch64-darwin: package 'treefmt'
│   ├───aarch64-linux: package 'treefmt'
│   ├───x86_64-darwin: package 'treefmt'
│   └───x86_64-linux: package 'treefmt'
├───legacyPackages
│   ├───aarch64-darwin omitted (use '--legacy' to show)
│   ├───aarch64-linux omitted (use '--legacy' to show)
│   ├───x86_64-darwin omitted (use '--legacy' to show)
│   └───x86_64-linux omitted (use '--legacy' to show)
├───nixosConfigurations
│   ├───build01: NixOS configuration
│   └───ghafhydra: NixOS configuration
├───nixosModules
│   ├───azure-common: NixOS module
│   ├───common: NixOS module
│   ├───generic-disk-config: NixOS module
│   ├───host-build01: NixOS module
│   ├───host-ghafhydra: NixOS module
│   ├───service-binary-cache: NixOS module
│   ├───service-hydra: NixOS module
│   ├───service-nginx: NixOS module
│   ├───service-openssh: NixOS module
│   ├───user-bmg: NixOS module
│   ├───user-builder: NixOS module
│   ├───user-hrosten: NixOS module
│   └───user-tester: NixOS module
├───overlays
└───packages
    ├───aarch64-darwin
    ├───aarch64-linux
    ├───x86_64-darwin
    └───x86_64-linux