Use unstable gerbil in pangolin module

modules/pangolin.nix

@@ -1,5 +1,8 @@
 {
   pkgs-unstable,
+  utils,
+  config,
+  lib,
   ...
 }: {
 
@@ -26,6 +29,13 @@
     };
   };
 
+  systemd.services.gerbil.serviceConfig.ExecStart = lib.mkForce (utils.escapeSystemdExecArgs [
+    (lib.getExe pkgs-unstable.fosrl-gerbil)
+    "--reachableAt=http://localhost:${toString config.services.gerbil.port}"
+    "--generateAndSaveKeyTo=${toString config.services.pangolin.dataDir}/config/key"
+    "--remoteConfig=http://localhost:3001/api/v1/gerbil/get-config"
+  ]);
+
 }
 
 # Settings needed on the host