@UnstableApi
    public TlsProvider tlsProvider() {
        return get(TLS_PROVIDER);
    }
Returns the {@link TlsProvider} which provides the {@link TlsKeyPair} that is used to create the
{@link SslContext} for TLS handshake.
core/src/main/java/com/linecorp/armeria/client/ClientFactoryOptions.java