revert bd3861c580

revert Merge pull request 'Remove clanModules/*' (#4202) from remove-modules into main

Reviewed-on: https://git.clan.lol/clan/clan-core/pulls/4202

See: https://git.clan.lol/clan/clan-core/issues/4365

Not all modules are migrated.
If they are not migrated, we need to write migration docs and please display the link to the migration docs

clanModules/packages/README.md

@@ -0,0 +1,5 @@
+---
+description = "Define package sets from nixpkgs and install them on one or more machines"
+categories = ["System"]
+features = [ "inventory", "deprecated" ]
+---

clanModules/packages/default.nix

@@ -0,0 +1,6 @@
+# Dont import this file
+# It is only here for backwards compatibility.
+# Dont author new modules with this file.
+{
+  imports = [ ./roles/default.nix ];
+}

clanModules/packages/roles/default.nix

@@ -0,0 +1,25 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+{
+  options.clan.packages = {
+    packages = lib.mkOption {
+      type = lib.types.listOf lib.types.str;
+      description = "The packages to install on the machine";
+    };
+  };
+  config = {
+
+    warnings = [
+      "The clan.packages module is deprecated and will be removed on 2025-07-15.
+      Please migrate to user-maintained configuration or the new equivalent clan services
+      (https://docs.clan.lol/reference/clanServices)."
+    ];
+    environment.systemPackages = map (
+      pName: lib.getAttrFromPath (lib.splitString "." pName) pkgs
+    ) config.clan.packages.packages;
+  };
+}