TLS Certificate Chain support

[notgne2]

There is a configuration field tls_certificate which can be configured to point to a PEM file, which does appear to in fact accept certificate chains, but it appears the entire chain but the certificate itself is discarded. The result of this is validation of a certificate not signed directly by a CA will always fail.

The code in build_acceptor seems to likely be where the additional certs are being discarded, and could probably be adapted with no additional changes to make TLS work correctly.

I am not aware of any way to work around this or anything I may have misconfigured.

[levkk]

Thanks for the report! If you have a minute, I'm happy to review a PR with the fix. No worries if not!