lift nix-serve out of servo

i'm going to enable it on desktop

machines/servo/default.nix

@@ -14,7 +14,6 @@
     ./services/matrix.nix
     ./services/navidrome.nix
     ./services/nginx.nix
-    ./services/nix-serve.nix
     ./services/pleroma.nix
     ./services/postfix.nix
     ./services/postgres.nix
@@ -28,6 +27,7 @@
   ];
   sane.impermanence.enable = true;
   sane.services.duplicity.enable = true;
+  sane.services.nixserve.enable = true;
 
   # TODO: look into the EFI stuff
   boot.loader.grub.enable = false;

machines/servo/services/nix-serve.nix

@@ -1,15 +0,0 @@
-# docs: https://nixos.wiki/wiki/Binary_Cache
-# to copy something to this machine's nix cache, do:
-#   nix copy --to ssh://nixcache.uninsane.org PACKAGE
-{ config, ... }:
-
-{
-  services.nix-serve = {
-    enable = true;
-    secretKeyFile = config.sops.secrets.nix_serve_privkey.path;
-  };
-
-  sops.secrets.nix_serve_privkey = {
-    sopsFile = ../../../secrets/servo.yaml;
-  };
-}

modules/default.nix

@@ -8,6 +8,7 @@
     ./impermanence.nix
     ./nixcache.nix
     ./services/duplicity.nix
+    ./services/nixserve.nix
     ./universal
   ];
 }

modules/services/nixserve.nix

@@ -0,0 +1,28 @@
+# docs: https://nixos.wiki/wiki/Binary_Cache
+# to copy something to this machine's nix cache, do:
+#   nix copy --to ssh://nixcache.uninsane.org PACKAGE
+{ config, lib, ... }:
+
+with lib;
+let
+  cfg = config.sane.services.nixserve;
+in
+{
+  options = {
+    sane.services.nixserve.enable = mkOption {
+      default = false;
+      type = types.bool;
+    };
+  };
+
+  config = mkIf cfg.enable {
+    services.nix-serve = {
+      enable = true;
+      secretKeyFile = config.sops.secrets.nix_serve_privkey.path;
+    };
+
+    sops.secrets.nix_serve_privkey = {
+      sopsFile = ../../secrets/servo.yaml;
+    };
+  };
+}