add yate service for autostart

config/hosts/yate/service.nix

@@ -0,0 +1,21 @@
+{ config, pkgs, ... }:
+
+{
+  systemd.services.yate = {
+    enable = true;
+    description = "Yate telehony engine";
+    unitConfig = {
+      Type = "simple";
+      After="network.target";
+    };
+    serviceConfig = {
+      ExecStart = "${pkgs.yate}/bin/yate -c /yate -e /yate/share -Do";
+      Type="simple";
+      Restart="always";
+      # ...
+    };
+    wantedBy = [ "default.target" ];
+    requiredBy = [ "network.target" ]; 
+    # ...
+  };
+}