@Override
    protected AccessTokenRequestContext extractInternal(
        final WebContext context,
        final AccessTokenRequestContext accessTokenRequestContext) {
        val challenge = getConfigurationContext().getObject().getRequestParameterResolver()
            .resolveRequestParameter(context, OAuth20Constants.CODE_VERIFIER).orElse(StringUtils.EMPTY);
        return accessTokenRequestContext.withCodeVerifier(challenge);
    }
This is {@link AccessTokenProofKeyCodeExchangeAuthorizationCodeGrantRequestExtractor}.

@author Misagh Moayyed
@since 6.0.0
support/cas-server-support-oauth-core-api/src/main/java/org/apereo/cas/support/oauth/web/response/accesstoken/ext/AccessTokenProofKeyCodeExchangeAuthorizationCodeGrantRequestExtractor.java