Introduce colmena config and add shairport-sync host

config/hosts/audio/configuration.nix

@@ -0,0 +1,10 @@
+{ pkgs, ... }:
+{
+  networking = {
+    hostName = "audio";
+  };
+
+  sound.enable = true;
+
+  system.stateVersion = "23.05";
+}

config/hosts/audio/default.nix

@@ -0,0 +1,7 @@
+{ ... }:
+{
+  imports = [
+    ./configuration.nix
+    ./shairport-sync.nix
+  ];
+}

config/hosts/audio/shairport-sync.nix

@@ -0,0 +1,8 @@
+{ ... }:
+{
+  services.shairport-sync = {
+    enable = true;
+    openFirewall = true;
+    arguments = "-vvv -o alsa -- -d plughw:1,0 -r 48000";
+  };
+}