nixos/sabnzbd: add package option

nixos/modules/services/networking/sabnzbd.nix

@@ -17,6 +17,13 @@ in
     services.sabnzbd = {
       enable = mkEnableOption "the sabnzbd server";
 
+      package = mkOption {
+        type = types.package;
+        default = pkgs.sabnzbd;
+        defaultText = "pkgs.sabnzbd";
+        description = "The sabnzbd executable package run by the service.";
+      };
+
       configFile = mkOption {
         type = types.path;
         default = "/var/lib/sabnzbd/sabnzbd.ini";
@@ -63,7 +70,7 @@ in
           GuessMainPID = "no";
           User = "${cfg.user}";
           Group = "${cfg.group}";
-          ExecStart = "${sabnzbd}/bin/sabnzbd -d -f ${cfg.configFile}";
+          ExecStart = "${lib.getBin cfg.package}/bin/sabnzbd -d -f ${cfg.configFile}";
         };
     };
   };