[machines] set dynamicdiscord binary cache

machines/configuration.nix

@@ -17,9 +17,21 @@ let
     {
       imports = [
         ({ pkgs, ... }: {
-          nix.extraOptions = ''
+          nix = {
-            experimental-features = nix-command flakes
+            extraOptions = ''
-          '';
+              experimental-features = nix-command flakes
+            '';
+
+            settings = {
+              substituters = [
+                "https://cache.dynamicdiscord.de"
+                "https://cache.nixos.org/"
+              ];
+              trusted-public-keys = [
+                "cache.dynamicdiscord.de-1:zWXTUJmfigHZ883fv52KZU6VFlivyNVVP2y7mvHtYeE="
+              ];
+            };
+          };
         })
 
         sops-nix.nixosModules.sops