refactor: add config.host option for host variables

modules/common/default.nix

@@ -12,6 +12,7 @@ in
 {
   imports = [
     inputs.home-manager.nixosModules.default
+    ./host.nix
   ];
 
   options.nixpkgs.allowedUnfree = lib.mkOption {

modules/common/host.nix

@@ -0,0 +1,13 @@
+{ lib, ... }:
+
+{
+  options.host = {
+    username = lib.mkOption {
+      type = lib.types.str;
+    };
+
+    name = lib.mkOption {
+      type = lib.types.str;
+    };
+  };
+}