Move arbi configuration file to secrets

modules/arbi/default.nix

@@ -1,4 +1,4 @@
-{ config, pkgs, ... }:
+{ config, ... }:
 let
   rev = "d531730d9640160f0519ef4b3640f8da49dd96f8";
   arbi-flake = builtins.getFlake "git+ssh://git@github.com/aciceri/arbi.git?rev=${rev}";
@@ -9,11 +9,7 @@ in
   services.arbi = {
     enable = true;
     log_level = "debug";
-    configFile = pkgs.writeText "arbi-config.kdl" ''
-      endpoint "wss://eth-mainnet.g.alchemy.com/v2/<REDACTED>"
-      pairs_file "pairs.json"
-      concurrency 4
-    '';
+    configFile = config.age.secrets.arbi-config.path;
   };
 
   environment.persistence."/persist".directories = [