The compose only forwarded VPN_SERVICE_PROVIDER, VPN_TYPE and the private
key, so Gluetun could not form a tunnel. Forward the peer public key,
endpoint IP/port, addresses, allowed IPs and keepalive interval. Add
matching placeholders to .env.example (current Gluetun uses the
single-peer WIREGUARD_* model, not the old WIREGUARD_PEERS_* names).