Fix license header and add changelog entry

Signed-off-by: Marc Handalian <[email protected]>

Author: mch2

CHANGELOG.md

@@ -28,6 +28,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Enabling term version check on local state for all ClusterManager Read Transport Actions ([#14273](https://github.com/opensearch-project/OpenSearch/pull/14273))
 - Add persian_stem filter (([#14847](https://github.com/opensearch-project/OpenSearch/pull/14847)))
 - Add rest, transport layer changes for hot to warm tiering - dedicated setup (([#13980](https://github.com/opensearch-project/OpenSearch/pull/13980))
+- Add basic aggregation support for derived fields ([#14618](https://github.com/opensearch-project/OpenSearch/pull/14618))
 
 ### Dependencies
 - Bump `org.gradle.test-retry` from 1.5.8 to 1.5.9 ([#13442](https://github.com/opensearch-project/OpenSearch/pull/13442))

server/src/test/java/org/opensearch/search/aggregations/bucket/terms/DerivedFieldAggregationTests.java

@@ -1,3 +1,11 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
 package org.opensearch.search.aggregations.bucket.terms;
 
 import org.apache.lucene.document.Document;