public static ConnectProxyConfig connect(
            InetSocketAddress proxyAddress, String username, String password, boolean useTls) {
        return connect(proxyAddress, username, password, HttpHeaders.of(), useTls);
    }
Creates a {@code ProxyConfig} configuration for CONNECT protocol.

@param proxyAddress the proxy address
@param username the username
@param password the password
@param useTls whether to use TLS to connect to the proxy
core/src/main/java/com/linecorp/armeria/client/proxy/ProxyConfig.java