Allow fields in BulkOperation to be optional (#378)

* Allow fields in BulkOperation to be optional

    https://opensearch.org/docs/1.3/api-reference/document-apis/bulk/#request-body
    > All actions support the same metadata: _index, _id, and _require_alias. If you don’t provide an ID, OpenSearch generates one automatically, which can make it challenging to update the document at a later time.

Signed-off-by: Cameron Durham <u64.cam@gmail.com>

CHANGELOG.md

@@ -38,6 +38,8 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 ### Dependencies
 ### Changed
 - Remove test artifacts from gh_pages workflow ([#335](https://github.com/opensearch-project/opensearch-js/issues/335))
+- Make fields in `BulkOperation` optional to match OpenSearch Bulk API requirements ([#378](https://github.com/opensearch-project/opensearch-js/pull/378))
+
 ### Deprecated
 ### Removed
 ### Fixed
@@ -57,4 +59,4 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 - Fix mutability of connection headers ([#291](https://github.com/opensearch-project/opensearch-js/issues/291))
 
 [2.1]: https://github.com/opensearch-project/opensearch-js/releases/tag/2.1.0
-[Unreleased]: https://github.com/opensearch-project/opensearch-js/compare/2.1...HEAD
+[Unreleased]: https://github.com/opensearch-project/opensearch-js/compare/2.1...HEAD

api/types.d.ts

@@ -40,12 +40,12 @@ export interface BulkIndexOperation extends BulkOperation { }
 export interface BulkIndexResponseItem extends BulkResponseItemBase { }
 
 export interface BulkOperation {
-  _id: Id;
-  _index: IndexName;
-  retry_on_conflict: integer;
-  routing: Routing;
-  version: VersionNumber;
-  version_type: VersionType;
+  _id?: Id;
+  _index?: IndexName;
+  retry_on_conflict?: integer;
+  routing?: Routing;
+  version?: VersionNumber;
+  version_type?: VersionType;
 }
 
 export interface BulkOperationContainer {