feat: add hosts and overlays module structure

.gitignore

@@ -11,5 +11,7 @@
 !/flake.lock
 
 !shells/
+!hosts/
+!overlays/
 
 !/flake/

flake.nix

@@ -95,9 +95,11 @@
       systems = import systems;
 
       imports = [
+        ./overlays
+        ./hosts
+        ./shells
         ./flake/formatter.nix
         ./flake/git-hooks.nix
-        ./shells
       ];
     };
 }

hosts/default.nix

@@ -0,0 +1,39 @@
+{
+  inputs,
+  config,
+  lib,
+  ...
+}:
+let
+  inherit (inputs.nixpkgs.lib) nixosSystem;
+
+  mkSystem =
+    {
+      host,
+      system,
+      extraModules ? [ ],
+      ...
+    }:
+    assert lib.assertMsg (lib.elem system config.systems)
+      "mkSystem: system '${system}' not in valid systems: ${lib.generators.toPretty { } config.systems}";
+    nixosSystem {
+      inherit system;
+      modules = [
+        {
+          networking.hostName = lib.mkDefault host;
+        }
+      ]
+      ++ extraModules;
+      specialArgs = { inherit inputs; };
+    };
+in
+{
+  flake.nixosConfigurations = {
+    nix-example = mkSystem {
+      host = "nix-example";
+      system = "x86_64-linux";
+      profile = "laptop";
+      extraModules = [ ];
+    };
+  };
+}

overlays/default.nix

@@ -0,0 +1 @@
+_: { }