automatically import ${namespace}.${class(es)} as modules

Allow to specify a list of classes in the host/<hostname>.nix (by
default the class <hostname> is used) that will automatically load
specified outputs of inputs.

export/nixosConfigurations.nix

@@ -15,6 +15,7 @@ let
     {
       namespace ? "fbs42",
       nixpkgs ? "nixpkgs",
+      classes ? [ hostname ],
     }:
     inputs.${nixpkgs}.lib.nixosSystem {
       specialArgs = { inherit inputs flake namespace; };
@@ -24,6 +25,9 @@ let
             base: builtins.attrValues (flake.lib.scan { base = "${base}/host/${hostname}"; })
           ) flake.lib.schema.base
         )
+        ++ map (class: {
+          imports = map (input: input.${namespace}.${class} or { }) (builtins.attrValues inputs);
+        }) classes
         ++ [ { config.networking.hostName = hostname; } ]
         ++ [ nixosModules.default ]
         ++ inputs.${nixpkgs}.lib.optional (inputs ? home-manager) {