loptland: modularize config a little by pulling out modules for gitea-runner and hydra

modules/nixos/services/hydra/default.nix

@@ -0,0 +1,37 @@
+{
+  lib,
+  config,
+  namespace,
+  ...
+}:
+let
+  cfg = config.${namespace}.services.hydra;
+  inherit (lib) mkIf mkOption mkEnableOption;
+in
+{
+  options.${namespace}.services.hydra = {
+    enable = mkEnableOption "Enable Hydra CI";
+    httpPort = mkOption {
+      type = lib.types.int;
+      default = 2000;
+      description = "The path to host the http server on, relevant for nginx forwarding";
+    };
+
+    enableCache = mkEnableOption "Enable cache using nix-server";
+  };
+
+  config = mkIf cfg.enable {
+    services.nix-serve = mkIf cfg.enableCache {
+      enable = true;
+      secretKeyFile = "/var/cache-priv-key.pem";
+    };
+
+    services.hydra = {
+      enable = true;
+      hydraURL = "http://localhost:${toString cfg.httpPort}";
+      port = cfg.httpPort;
+      notificationSender = "hydra@localhost";
+      useSubstitutes = true;
+    };
+  };
+}