Move nix code under nix/

nix/modules/default.nix

@@ -0,0 +1,57 @@
+{ lib, pkgs, ... }:
+
+let
+  service-1 = "service-1";
+  service-2 = "service-2";
+
+  services = {
+    ${service-1} = {
+      enable = true;
+      description = service-1;
+      wants = [ "network-online.target" ];
+      after = [
+        "network-online.target"
+        "avahi-daemon.service"
+        "chrony.service"
+        "nss-lookup.target"
+        "tinc.service"
+        "pulseaudio.service"
+      ];
+      serviceConfig = {
+        Type = "oneshot";
+        RemainAfterExit = true;
+        script = ''
+          true
+        '';
+        ExecReload = "true";
+      };
+      wantedBy = [ "multi-user.target" ];
+    };
+
+    ${service-2} = {
+      enable = true;
+      description = service-2;
+      serviceConfig = {
+        Type = "simple";
+      };
+      partOf = [ "${service-1}.service" ];
+      wantedBy = [ "${service-1}.service" ];
+
+      script = ''
+        true
+      '';
+    };
+  };
+in
+{
+  options = {
+    service-manager.services = lib.mkOption {
+      type = with lib.types; listOf str;
+    };
+  };
+
+  config = {
+    service-manager.services = lib.attrNames services;
+    systemd = { inherit services; };
+  };
+}