public EsIndexProperties build() {
            Preconditions.checkArgument(propertiesMap.size() > 0, "Must add at least one property");
            return new EsIndexProperties(this);
        }
Build and validate instance of {@link EsIndexProperties}
@return a new {@link EsIndexProperties} with the configuration provided in this builder
common/es/src/main/java/io/apiman/common/es/util/builder/index/EsIndexProperties.java