public String errorOpenIDConfiguration() {
        return errorOpenIDConfiguration;
    }
Return the (potentially null) error openid-configuration value as per
<a href="https://tools.ietf.org/html/rfc7628#section-3.2.2">RFC 7628: A Set
of Simple Authentication and Security Layer (SASL) Mechanisms for OAuth</a>.

@return the (potentially null) error openid-configuration value
clients/src/main/java/org/apache/kafka/common/security/oauthbearer/OAuthBearerValidatorCallback.java