update changelog

Author: jonhealy1

CHANGELOG.md

@@ -10,6 +10,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Added
 
 - Added catalogs route support to enable federated hierarchical catalog browsing and navigation in the STAC API. [#547](https://github.com/stac-utils/stac-fastapi-elasticsearch-opensearch/pull/547)
+- Added DELETE `/catalogs/{catalog_id}/collections/{collection_id}` endpoint to support removing collections from catalogs. When a collection belongs to multiple catalogs, it removes only the specified catalog from the collection's parent_ids. When a collection belongs to only one catalog, the collection is deleted entirely. [#554](https://github.com/stac-utils/stac-fastapi-elasticsearch-opensearch/pull/554)
+- Added `parent_ids` internal field to collections to support multi-catalog hierarchies. Collections can now belong to multiple catalogs, with parent catalog IDs stored in this field for efficient querying and management. [#554](https://github.com/stac-utils/stac-fastapi-elasticsearch-opensearch/pull/554)
 
 ### Changed