@Override
    public Map<String, EsIndexProperties> getEsIndices() {
        Map<String, EsIndexProperties> indexes = super.getEsIndices();
        indexes.put(EsConstants.INDEX_DATA_VERSION,
            EsIndexProperties.builder()
                .addProperty(EsConstants.ES_FIELD_ORGANIZATION_ID, EsIndexUtils.KEYWORD_PROP)
                .addProperty(EsConstants.ES_FIELD_UPDATED_ON, EsIndexUtils.DATE_PROP)
                .addProperty(EsConstants.ES_FIELD_VERSION, EsIndexUtils.LONG_PROP)
            .build()
        );
        return indexes;
    }
Checks the ES store to see if the 'dataVersion' entry has been updated with a newer
version #.  If it has, then we need to invalidate our cache.
gateway/engine/es/src/main/java/io/apiman/gateway/engine/es/PollCachingEsRegistry.java