add watchdog service

modules/watchdog/default.nix

@@ -0,0 +1,24 @@
+{ lib, pkgs, config, ...}:
+let
+  inherit (lib) mkOption types;
+  inherit (pkgs) liminix;
+in
+{
+  options = {
+    system.service.watchdog =  mkOption {
+      type = liminix.lib.types.serviceDefn;
+    };
+  };
+  config.system.service.watchdog = liminix.callService ./watchdog.nix {
+    watched = mkOption {
+      description = "services to watch";
+      type = types.listOf liminix.lib.types.service;
+    };
+    headStart = mkOption {
+      description = "delay in seconds before watchdog starts checking service health";
+      default = 60;
+      type = types.int;
+    };
+  };
+  config.kernel.config.WATCHDOG = "y";
+}