@Override
    public Optional<String> extract(final Authentication authentication,
                                    final HttpServletRequest request,
                                    final HttpServletResponse response) {
        return Optional.ofNullable(HttpRequestUtils.getHttpServletRequestUserAgent(request));
    }
Provides the User Agent for device fingerprint generation.

@author Daniel Frett
@since 5.3.0
support/cas-server-support-trusted-mfa-core/src/main/java/org/apereo/cas/trusted/web/flow/fingerprint/UserAgentDeviceFingerprintExtractor.java