Turn off the display when system is suspended on lid close

This patch is adding two systemd services.
On suspend we turn off the display of gui-vm and on
resume we turn on the display back. This will help to
save system power when system system is suspended or lid
is closed.

Signed-off-by: Vunny Sodhi <vunny.sodhi@unikie.com>

modules/host/default.nix

@@ -3,7 +3,7 @@
 #
 # Modules that should be only imported to host
 #
-{ lib, ... }:
+{ lib, pkgs, ... }:
 {
   networking.hostName = lib.mkDefault "ghaf-host";
 
@@ -15,4 +15,27 @@
     # To push logs to central location
     ../common/logging/client.nix
   ];
+
+  # Adding below systemd services to save power by turning off display when system is suspended / lid close
+  systemd.services.display-suspend = {
+    enable = true;
+    description = "Display Suspend Service";
+    serviceConfig = {
+      Type = "oneshot";
+      ExecStart = ''${pkgs.sshpass}/bin/sshpass -p ghaf ${pkgs.openssh}/bin/ssh -o StrictHostKeyChecking=no ghaf@gui-vm-debug WAYLAND_DISPLAY=/run/user/1000/wayland-0 wlopm --off \* '';
+    };
+    wantedBy = [ "sleep.target" ];
+    before = [ "sleep.target" ];
+  };
+
+  systemd.services.display-resume = {
+    enable = true;
+    description = "Display Resume Service";
+    serviceConfig = {
+      Type = "oneshot";
+      ExecStart = ''${pkgs.sshpass}/bin/sshpass -p ghaf ${pkgs.openssh}/bin/ssh -o StrictHostKeyChecking=no ghaf@gui-vm-debug WAYLAND_DISPLAY=/run/user/1000/wayland-0 wlopm --on \* '';
+    };
+    wantedBy = [ "suspend.target" ];
+    after = [ "suspend.target" ];
+  };
 }