feat(nix): add marpa as binary cache for Nix

system/default.nix

@@ -47,16 +47,16 @@ in {
 
     nix.settings = {
       substituters = [
-        "https://nix-community.cachix.org?priority=10"
-        "https://devenv.cachix.org?priority=20"
-        "https://phundrak.cachix.org?priority=30"
+        "http://marpa:5000?priority=5"
+        "https://phundrak.cachix.org?priority=10"
+        "https://nix-community.cachix.org?priority=20"
         "https://cache.nixos.org?priority=40"
       ];
       trusted-public-keys = [
-        "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
-        "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
-        "devenv.cachix.org-1:w1cLUi8dv3hnoSPGAuibQv+f9TZLr6cv/Hm9XgU50cw="
+        "marpa-local:XoO+dFN4PeauF52pYuy3Vh4Sdtl2qIdxu5aUasWKv6Q="
         "phundrak.cachix.org-1:osJAkYO0ioTOPqaQCIXMfIRz1/+YYlVFkup3R2KSexk="
+        "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
+        "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
       ];
       http-connections = 128;
       experimental-features = [

system/services/default.nix

@@ -3,6 +3,7 @@
     ./calibre.nix
     ./endlessh.nix
     ./fwupd.nix
+    ./harmonia.nix
     ./jellyfin.nix
     ./languagetool.nix
     ./plex.nix

system/services/harmonia.nix

@@ -0,0 +1,36 @@
+{
+  config,
+  lib,
+  ...
+}:
+with lib; let
+  cfg = config.mySystem.services.harmonia;
+in {
+  options.mySystem.services.harmonia = {
+    enable = mkEnableOption "Harmonia Nix binary cache server";
+    port = mkOption {
+      type = types.port;
+      default = 5000;
+      description = "Port to listen on";
+    };
+    priority = mkOption {
+      type = types.ints.between 0 100;
+      default = 50;
+      description = "Cache priority (lower = higher priority, 0-100)";
+    };
+    signKeyPaths = mkOption {
+      type = types.listOf types.path;
+      description = "Paths to the signing keys to use for signing the cache.";
+    };
+  };
+  config = mkIf cfg.enable {
+    services.harmonia.cache = {
+      enable = true;
+      inherit (cfg) signKeyPaths;
+      settings = {
+        inherit (cfg) priority;
+        bind = "[::]:${toString cfg.port}";
+      };
+    };
+  };
+}