public TlsProviderBuilder keyPair(TlsKeyPair tlsKeyPair) {
        return keyPair("*", tlsKeyPair);
    }
Sets the default {@link TlsKeyPair} which is used when no {@link TlsKeyPair} is specified for a hostname.

<p>The {@link TlsKeyPair} will be used for
<a href="https://www.cloudflare.com/learning/access-management/what-is-mutual-tls/">client certificate authentication</a>
when it is used for a client.
core/src/main/java/com/linecorp/armeria/common/TlsProviderBuilder.java