Add NixOS binary cache

modules/binary-cache.nix

@@ -0,0 +1,34 @@
+{ config, ... }:
+{
+
+  sops.secrets = {
+    nixCacheKey = {
+      owner = config.services.borgbackup.jobs.data.user;
+      key = "nix/cache_secret_key";
+    };
+  };
+
+
+  services.nix-serve = {
+    enable = true;
+    port = 1500;
+    secretKeyFile = config.sops.secrets.nixCacheKey.path;
+  };
+
+  services.nginx = {
+    virtualHosts = {
+      "cache.${config.networking.domain}" = {
+
+        enableACME = true;
+        forceSSL = true;
+
+        locations."/".extraConfig = ''
+          proxy_pass http://localhost:${toString config.services.nix-serve.port};
+          proxy_set_header Host $host;
+          proxy_set_header X-Real-IP $remote_addr;
+          proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        '';
+      };
+    };
+  };
+}