@UnstableApi
    public static ConnectProxyConfig connect(
            InetSocketAddress proxyAddress, HttpHeaders headers, boolean useTls) {
        requireNonNull(proxyAddress, "proxyAddress");
        return new ConnectProxyConfig(proxyAddress, null, null, headers, useTls);
    }
Creates a {@code ProxyConfig} configuration for CONNECT protocol.

@param proxyAddress the proxy address
@param headers the {@link HttpHeaders} to send to the proxy
@param useTls whether to use TLS to connect to the proxy
core/src/main/java/com/linecorp/armeria/client/proxy/ProxyConfig.java