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/auto-upgrade/README.md

@@ -0,0 +1,8 @@
+---
+description = "Set up automatic upgrades"
+categories = ["System"]
+features = [ "inventory", "deprecated" ]
+---
+
+Whether to periodically upgrade NixOS to the latest version. If enabled, a
+systemd timer will run `nixos-rebuild switch --upgrade` once a day.

clanModules/auto-upgrade/roles/default.nix

@@ -0,0 +1,32 @@
+{
+  config,
+  lib,
+  ...
+}:
+let
+  cfg = config.clan.auto-upgrade;
+in
+{
+  options.clan.auto-upgrade = {
+    flake = lib.mkOption {
+      type = lib.types.str;
+      description = "Flake reference";
+    };
+  };
+
+  config = {
+
+    warnings = [
+      "The clan.auto-upgrade 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)."
+    ];
+
+    system.autoUpgrade = {
+      inherit (cfg) flake;
+      enable = true;
+      dates = "02:00";
+      randomizedDelaySec = "45min";
+    };
+  };
+}