Get back ExternalUrl for SSH connection

docker-compose-generator/docker-fragments/btcpayserver.yml

@@ -12,6 +12,7 @@ services:
       BTCPAY_POSTGRES: User ID=postgres;Host=postgres;Port=5432;Database=btcpayserver${NBITCOIN_NETWORK:-regtest}
       BTCPAY_NETWORK: ${NBITCOIN_NETWORK:-regtest}
       BTCPAY_BIND: 0.0.0.0:49392
+      BTCPAY_EXTERNALURL: ${BTCPAY_PROTOCOL:-https}://${BTCPAY_HOST}/
       BTCPAY_ROOTPATH: ${BTCPAY_ROOTPATH:-/}
       BTCPAY_SSHTRUSTEDFINGERPRINTS: ${BTCPAY_SSHTRUSTEDFINGERPRINTS}
       BTCPAY_SSHKEYFILE: ${BTCPAY_SSHKEYFILE}