private String getClientId() {
        return NullSafe.getOrElseGet(
                clientCredentials,
                ClientCredentials::getClientId,
                openIdConfiguration::getClientId);
    }
Allows you do define client credentials that differ from those in {@link OpenIdConfiguration}
stroom-security/stroom-security-common-impl/src/main/java/stroom/security/common/impl/OpenIdTokenRequestHelper.java