Add systemd hardening to sso-server

debian/sso-server.service

 [Unit]
 Description=SSO Server
-After=auth-server.socket
+After=network.target auth-server.socket
 
 [Service]
 User=sso-server
@@ -9,6 +9,15 @@ EnvironmentFile=-/etc/default/sso-server
 ExecStart=/usr/bin/sso-server --addr $ADDR
 Restart=always
 
+# Hardening
+NoNewPrivileges=yes
+PrivateTmp=yes
+PrivateDevices=yes
+ProtectHome=yes
+ProtectSystem=full
+ReadOnlyDirectories=/
+CapabilityBoundingSet=CAP_NET_BIND_SERVICE
+
 [Install]
 WantedBy=multi-user.target