private Set<String> getValidIssuers(final AbstractOpenIdConfig openIdConfig) {
        final Set<String> validIssuers = new HashSet<>();
        if (!NullSafe.isBlankString(openIdConfig.getIssuer())) {
            validIssuers.add(openIdConfig.getIssuer());
        }
        validIssuers.addAll(NullSafe.set(openIdConfig.getValidIssuers()));
        LOGGER.debug(() -> LogUtil.message("Valid issuers:\n{}", String.join("\n", validIssuers)));
        return validIssuers;
    }
Combines the values from {@link AbstractOpenIdConfig} with values obtained from the external
Open ID Connect IDP server.
stroom-security/stroom-security-common-impl/src/main/java/stroom/security/common/impl/ExternalIdpConfigurationProvider.java