refactor: merge 'audio-automation' module into 'audio' module

modules/audio/audio-automation.nix

@@ -0,0 +1,29 @@
+{
+  lib,
+  config,
+  pkgs,
+  ...
+}:
+
+let
+  cfg = config.audio.automation;
+in
+{
+  options.audio.automation.enable = lib.mkEnableOption "audio automation (mute on battery)";
+
+  config = lib.mkIf cfg.enable {
+    environment.systemPackages = [ pkgs.libnotify ];
+
+    services.udev.extraRules = ''
+      SUBSYSTEM=="power_supply", ATTR{online}=="0", ACTION=="change", TAG+="systemd", ENV{SYSTEMD_USER_WANTS}+="mute-audio.service"
+    '';
+
+    systemd.user.services.mute-audio = {
+      description = "mute audio when switching to battery power";
+      serviceConfig = {
+        Type = "oneshot";
+        ExecStart = "${pkgs.bash}/bin/bash -c '${pkgs.pulseaudio}/bin/pactl set-sink-mute $(${pkgs.pulseaudio}/bin/pactl get-default-sink) true && ${pkgs.libnotify}/bin/notify-send \"audio Muted\" \"switched to battery power\"'";
+      };
+    };
+  };
+}