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/pipewire.nix

@@ -0,0 +1,25 @@
+# Sources for this configuration:
+# - https://nixos.wiki/wiki/PipeWire
+
+{ config, pkgs, lib, ... }:
+
+with lib;
+
+let
+
+  cfg = config.ccchh.services.audio;
+
+in
+
+{
+  config = mkIf cfg.enable {
+    security.rtkit.enable = true;
+    services.pipewire = {
+      enable = true;
+      systemWide = true;
+      alsa.enable = true;
+      alsa.support32Bit = true;
+      pulse.enable = true;
+    };
+  };
+}