nix flake show does not exit cleanly

[sarcasticadmin]

Description

Related to: #598

$ nix flake show
git+file:///home/rherna/workspace/scale-network?ref=refs%2fheads%2fadd-makefile&rev=e194d74ec0ddc4116db4459276c7c49b4b289a82
├───devShells
│   └───x86_64-linux
│       └───default: development environment 'nix-shell'
├───nixosConfigurations
│   ├───coreMaster: NixOS configuration
│   ├───coreSlave: NixOS configuration
│   ├───loghost: NixOS configuration
│   ├───massflash: NixOS configuration
│   └───signs: NixOS configuration
├───overlays
│   └───default: Nixpkgs overlay
└───packages
    └───x86_64-linux
        ├───scaleInventory: package 'scaleInventory'
error: expected a derivation

This seems to be due to scaleTests being a new scope instead of an individual package: https://github.com/socallinuxexpo/scale-network/blob/280bc083828adec400c6f43f1493ee210acfbbf6/flake.nix Ideally it would be nice to not have to explicitly define each package in the scope.

Interesting discussions around doing this: https://discourse.nixos.org/t/namespacing-scoping-a-group-of-packages/13782/2

Acceptance Criteria

• nix flake show exits cleanly
• all tests defined in scaleTests are still callable