because this metabase now needs SNI properly configured, which means that the backend must know the frontend domain name and can not be accessed by its IP address, we stop serving https on IPv6 directly from metabase's embedded jetty and reconfigure it to serve http on IPv4 and add an haproxy instance to serve https on IPv6. This is just an "internal" change because the external IP will be same and the certificate is still a self-signed one for now.
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