Add esql version

Adds a `version` parameter to the ESQL `_query` request endpoint. We'll
do some work to give this a default value in the generated clients soon,
but for 8.14+ this'll be a required parameter.

specification/esql/_types/Version.ts

@@ -0,0 +1,34 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import { integer } from '@_types/Numeric'
+import { Duration } from '@_types/Time'
+
+export enum Version {
+    /**
+     * Run against the first version of ESQL.
+     */
+    '2024.04.01',
+    /**
+     * Run against the unreleased version of the ESQL language. This will
+     * contain any changes staged for release that have yet to be included
+     * in a version.
+     */
+    snapshot
+}

specification/esql/query/QueryRequest.ts

@@ -20,6 +20,7 @@
 import { RequestBase } from '@_types/Base'
 import { QueryContainer } from '@_types/query_dsl/abstractions'
 import { ScalarValue } from '@_types/common'
+import { Version } from '@esql/_types/Version'
 
 /**
  * Executes an ES|QL request
@@ -59,6 +60,10 @@ export interface Request extends RequestBase {
     /**
      * The ES|QL query API accepts an ES|QL query string in the query parameter, runs it, and returns the results.
      */
-    query: string
+    query: string,
+    /**
+     * The version of the ES|QL language in which the "query" field uses was written.
+     */
+    version: Version
   }
 }