DateRangeBucket
data class DateRangeBucket<T>(val key: String, val docCount: Long, val from: Double? = null, val fromAsString: String? = null, val fromAsDatetime: T? = null, val to: Double? = null, val toAsString: String? = null, val toAsDatetime: T? = null, val aggs: Map<String, AggregationResult> = emptyMap()) : KeyedBucket<String>