Move audio configuration into a service module

- Move audio configuration into a service module to make it easily
  usable by multiple hosts.
- Allow configuration of AirPlay 2 name.
- Don't set MQTT topic of Shairport-Sync (AirPlay 2) explictly. Defaults
  to hostname now.
- Don't set sound.enable anymore, since its not needed.

modules/services/audio/default.nix

@@ -0,0 +1,35 @@
+{ config, pkgs, lib, ... }:
+
+with lib;
+
+let
+
+  cfg = config.ccchh.services.audio;
+
+in
+
+{
+  imports = [
+    ./librespot.nix
+    ./networking.nix
+    ./pipewire.nix
+    ./shairport-sync.nix
+  ];
+
+  options = {
+    ccchh.services.audio = {
+      enable = mkEnableOption (lib.mdDoc "audio");
+
+      name = mkOption {
+        type = types.str;
+        example = "Audio Living Room";
+        default = config.networking.hostName;
+        defaultText = literalExpression "config.networking.HostName";
+        description = lib.mdDoc ''
+          The name to use for display in the various audio services. For example
+          the name of the displayed Spotify speaker or AirPlay audio device.
+        '';
+      };
+    };
+  };
+}