added systemd unit for setting iptables rules using added script, added DSNet systemd unit

roles/init-server/files/usr/local/bin/dsnet-forward.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+set -euo pipefail
+
+if [[ "$1" == "start" ]]; then
+    /usr/sbin/iptables -A FORWARD -i dsnet -p tcp --sport {80,443,465,587,995,110,143,993} -j ACCEPT
+    /usr/sbin/iptables -t nat -A POSTROUTING -o dsnet -j MASQUERADE
+elif [[ "$1" == "stop" ]]; then
+    /usr/sbin/iptables -D FORWARD -i dsnet -p tcp --sport {80,443,465,587,995,110,143,993} -j ACCEPT
+    /usr/sbin/iptables -t nat -D POSTROUTING -o dsnet -j MASQUERADE
+fi