feat(cache): add cache service

modules/nixos/sites/cache/default.nix

@@ -0,0 +1,37 @@
+{
+  lib,
+  config,
+  pkgs,
+  ...
+}:
+with lib;
+with lib.custom; let
+  cfg = config.sites.cache;
+
+  sec = config.age.secrets;
+in {
+  options.sites.hydra = with types; {
+    enable = mkBoolOpt false "Enable Hydra";
+  };
+
+  config = mkIf cfg.enable {
+    age.secrets = {
+      cache_key = {
+        file = ./sec/cache_key.age;
+      };
+    };
+
+    services.nix-serve = {
+      enable = true;
+      secretKeyFile = sec.cache_key.path;
+    };
+
+    services.nginx.virtualHosts."cache.zoeys.computer" = {
+      forceSSL = true;
+      enableACME = true;
+      locations."/" = {
+        proxyPass = "http://${config.services.nix-serve.bindAddress}:${toString config.services.nix-serve.port}";
+      };
+    };
+  };
+}