Add time series aggregation (#2862)

(cherry picked from commit be63cfc)

Author: pquentin

specification/_doc_ids/table.csv

@@ -494,6 +494,7 @@ search-aggregations-metrics-string-stats-aggregation,https://www.elastic.co/guid
 search-aggregations-metrics-sum-aggregation,https://www.elastic.co/guide/en/elasticsearch/reference/{branch}/search-aggregations-metrics-sum-aggregation.html
 search-aggregations-pipeline-sum-bucket-aggregation,https://www.elastic.co/guide/en/elasticsearch/reference/{branch}/search-aggregations-pipeline-sum-bucket-aggregation.html
 search-aggregations-bucket-terms-aggregation,https://www.elastic.co/guide/en/elasticsearch/reference/{branch}/search-aggregations-bucket-terms-aggregation.html
+search-aggregations-bucket-time-series-aggregation,https://www.elastic.co/guide/en/elasticsearch/reference/{branch}/search-aggregations-bucket-time-series-aggregation.html
 search-aggregations-metrics-top-hits-aggregation,https://www.elastic.co/guide/en/elasticsearch/reference/{branch}/search-aggregations-metrics-top-hits-aggregation.html
 search-aggregations-metrics-ttest-aggregation,https://www.elastic.co/guide/en/elasticsearch/reference/{branch}/search-aggregations-metrics-ttest-aggregation.html
 search-aggregations-metrics-top-metrics,https://www.elastic.co/guide/en/elasticsearch/reference/{branch}/search-aggregations-metrics-top-metrics.html

specification/_types/aggregations/Aggregate.ts

@@ -108,6 +108,7 @@ export type Aggregate =
   | UnmappedSignificantTermsAggregate
   | CompositeAggregate
   | FrequentItemSetsAggregate
+  | TimeSeriesAggregate
   //
   | ScriptedMetricAggregate
   | TopHitsAggregate
@@ -648,6 +649,14 @@ export class FrequentItemSetsBucket extends MultiBucketBase {
   support: double
 }
 
+/** @variant name=time_series */
+export class TimeSeriesAggregate extends MultiBucketAggregateBase<TimeSeriesBucket> {}
+
+export class TimeSeriesBucket extends MultiBucketBase {
+  key: Dictionary<Field, FieldValue>
+  doc_count: long
+}
+
 //----- Misc
 
 /** @variant name=scripted_metric */

specification/_types/aggregations/AggregationContainer.ts

@@ -481,6 +481,14 @@ export class AggregationContainer {
    * @doc_id search-aggregations-bucket-terms-aggregation
    */
   terms?: TermsAggregation
+  /**
+   * The time series aggregation queries data created using a time series index.
+   * This is typically data such as metrics or other data streams with a time component, and requires creating an index using the time series mode.
+   * @doc_id search-aggregations-bucket-time-series-aggregation
+   * @availability stack stability=experimental
+   * @availability serverless stability=experimental
+   */
+  time_series?: TimeSeriesAggregation
   /**
    * A metric aggregation that returns the top matching documents per bucket.
    * @doc_id search-aggregations-metrics-top-hits-aggregation

specification/_types/aggregations/bucket.ts

@@ -976,6 +976,18 @@ export class TermsAggregation extends BucketAggregationBase {
   format?: string
 }
 
+export class TimeSeriesAggregation extends BucketAggregationBase {
+  /**
+   * The maximum number of results to return.
+   * @server_default 10000
+   */
+  size?: integer
+  /**
+   * Set to `true` to associate a unique string key with each bucket and returns the ranges as a hash rather than an array.
+   */
+  keyed?: boolean
+}
+
 // Note: ES is very lazy when parsing this data type: it accepts any number of properties in the objects below,
 // but will only keep the *last* property in JSON document order and ignore others.
 // This means that something like `"order": { "downloads": "desc", "_key": "asc" }` will actually be interpreted