@Override
    public void processChallenge(
            final AuthChallenge authChallenge,
            final HttpContext context) throws MalformedChallengeException {
        Args.notNull(authChallenge, "AuthChallenge");
        this.paramMap.clear();
        final List<NameValuePair> params = authChallenge.getParams();
        if (params != null) {
            for (final NameValuePair param: params) {
                this.paramMap.put(param.getName().toLowerCase(Locale.ROOT), param.getValue());
            }
        }
        if (this.paramMap.isEmpty()) {
            throw new MalformedChallengeException("Missing digest auth parameters");
        }

        final String userHashValue = this.paramMap.get("userhash");
        this.userhashSupported = "true".equalsIgnoreCase(userHashValue);

        this.complete = true;
    }
@deprecated This constructor is deprecated to enforce the use of {@link StandardCharsets#UTF_8} encoding
in compliance with RFC 7616 for HTTP Digest Access Authentication. Use the default constructor {@link #DigestScheme()} instead.

@param charset the {@link Charset} set to be used for encoding credentials. This parameter is ignored as UTF-8 is always used.
httpclient5/src/main/java/org/apache/hc/client5/http/impl/auth/DigestScheme.java