refactor: rename modules to nixosModules

nixosModules/flake-module.nix

@@ -0,0 +1,28 @@
+{ lib, ... }:
+{
+  flake.nixosModules =
+    (
+      (builtins.readDir ./.)
+      |> lib.filterAttrs (path: type: type == "regular" && (lib.hasSuffix ".nix" path))
+      |> lib.mapAttrs' (
+        path: _: {
+          name = lib.removeSuffix ".nix" path;
+          value = {
+            imports = [ ./${path} ];
+          };
+        }
+      )
+    )
+    // {
+      server.imports = [
+        ./motd.nix
+      ];
+
+      common.imports = [
+        {
+          users.mutableUsers = lib.mkDefault false;
+          services.userborn.enable = lib.mkDefault true;
+        }
+      ];
+    };
+}