Fix asterisk-sounds-de

There was a race condition that lead to incorrect user permissions on
the sounds directory. The solution to use the preStart script is better
and fixes this issue as well.

hosts/aluminium/services/asterisk.nix

@@ -172,14 +172,6 @@ in
     ];
   };
 
-  system.activationScripts.symlink-asterisk-sounds-de = lib.stringAfter [ "var" ] ''
-    sounds="/var/lib/asterisk/sounds"
-    sounds_de="$sounds/de"
-    mkdir -p "$sounds"
-    [ -L "$sounds_de" ] && rm "$sounds_de"
-    ln -s "${pkgs.asterisk-sounds-de}/" "$sounds_de"
-  '';
-
   systemd.services."asterisk-reload-endpoint@" = {
     description = "Check if asterisk endpoint is identified and reload it when it is not.";
     serviceConfig = {

pkgs/asterisk-sounds-de/module.nix

@@ -0,0 +1,15 @@
+{ config, lib, pkgs, ... }:
+
+let cfg = config;
+in
+{
+  config = lib.mkIf cfg.services.asterisk.enable {
+    systemd.services.asterisk.preStart = lib.mkMerge [
+      (lib.mkAfter ''
+        sounds_de="/var/lib/asterisk/sounds/de"
+        [ -L "$sounds_de" ] && rm "$sounds_de"
+        ln -s "${pkgs.asterisk-sounds-de}/" "$sounds_de"
+      '')
+    ];
+  };
+}

pkgs/default.nix

@@ -6,7 +6,7 @@ let
 in
 {
   ariang = callPackage ./ariang { };
-  asterisk-sounds-de = callPackage ./asterisk/sounds-de.nix { };
+  asterisk-sounds-de = callPackage ./asterisk-sounds-de { };
   docker-machine-driver-hetzner = callPackage ./docker-machine-driver-hetzner {
     inherit (inputs.gomod2nix.legacyPackages.${system}) buildGoApplication;
   };

pkgs/modules.nix

@@ -2,6 +2,7 @@
 
 {
   imports = [
+    ./asterisk-sounds-de/module.nix
     ./myintercom-doorbell/module.nix
     ./pretix/module.nix
   ];