Updated client name input restrictions and hint

openvpn-install.sh

@@ -1052,9 +1052,9 @@ verb 3" >>/etc/openvpn/client-template.txt
 function newClient() {
 	echo ""
 	echo "Tell me a name for the client."
-	echo "Use one word only, no special characters."
+	echo "The name must consist of alphanumeric character. It may also include an underscore or a dash."
 
-	until [[ $CLIENT =~ ^[a-zA-Z0-9_]+$ ]]; do
+	until [[ $CLIENT =~ ^[a-zA-Z0-9_-]+$ ]]; do
 		read -rp "Client name: " -e CLIENT
 	done