@Nullable
    default List<X509Certificate> trustedCertificates(String hostname) {
        return null;
    }
Returns trusted certificates for verifying the remote endpoint's certificate.

<p>If no matching {@link X509Certificate}s are found for a hostname, {@code "*"} will be specified to get
the default {@link X509Certificate}s.
The system default will be used if this method returns null.

<p>Note that this operation is executed in an event loop thread, so it should not be blocked.
core/src/main/java/com/linecorp/armeria/common/TlsProvider.java