public EsField build() {
            checkArgument(type != null || ignoreAbove != null, "At least one of the fields type or ignoreAbove must non-null");
            checkArgument(ignoreAbove == null || ignoreAbove > 0, "ignore_above must be greater than zero");
            return new EsField(this);
        }
Build and validate instance of {@link EsField}
@return a new {@link EsField} with the configuration provided in this builder
common/es/src/main/java/io/apiman/common/es/util/builder/index/EsField.java