public boolean isChallengeExpected(final AuthExchange authExchange) {
        final AuthScheme authScheme = authExchange.getAuthScheme();
        return authScheme != null && authScheme.isChallengeExpected();
    }
Determines if the scheme requires an auth challenge for responses that do not
have a challenge HTTP code. (i.e whether it needs a mutual authentication token)
httpclient5/src/main/java/org/apache/hc/client5/http/impl/auth/AuthenticationHandler.java