private Response doPost(final Invocation.Builder invocationBuilder) {
        LOGGER.debug("State: {}", this);
        if (openIdConfiguration.isFormTokenRequest()) {
            return doFormPost(invocationBuilder);
        } else {
            return doJsonPost(invocationBuilder);
        }
    }
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