This addition requires usage of `DEFAULT_HOST` on containers tested to ensure they don't accidentally use `web2` as their default fallback (due to no SNI / `-servername` requested in openssl queries), otherwise they would be testing against the incorrect DH params response.
They could alternatively request an FQDN explicitly as well, instead of relying on implicit fallback/default server selection behaviour.
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`web2.nginx-proxy.tld.dhparam.pem` is a copy of `ffdhe2048.pem`.
