Blocking bulk_items endpoint when ENABLE_DATETIME_INDEX_FILTERING (#438)

**Description:**
The `/collections/{collection_id}/bulk_items` endpoint does not work
when `ENABLE_DATETIME_INDEX_FILTERING` is set to true, as only the async
`/collections/{collection_id}/items` version was implemented while the
sync `/collections/{collection_id}/bulk_items` wasn't. This PR blocks
the /bulk_items endpoint when `ENABLE_DATETIME_INDEX_FILTERING` is set
to true.

**PR Checklist:**

- [x] Code is formatted and linted (run `pre-commit run --all-files`)
- [x] Tests pass (run `make test`)
- [ ] Documentation has been updated to reflect changes, if applicable
- [x] Changes are added to the changelog

---------

Co-authored-by: Jonathan Healy <jonathan.d.healy@gmail.com>

Author: z-mrozu

CHANGELOG.md

@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Changed
 
 - Changed assets serialization to prevent mapping explosion while allowing asset inforamtion to be indexed. [#341](https://github.com/stac-utils/stac-fastapi-elasticsearch-opensearch/pull/341)
+- Blocked the /collections/{collection_id}/bulk_items endpoint when environmental variable ENABLE_DATETIME_INDEX_FILTERING is set to true. [#438](https://github.com/stac-utils/stac-fastapi-elasticsearch-opensearch/pull/438)
 
 ### Fixed
 

stac_fastapi/core/stac_fastapi/core/core.py

@@ -965,6 +965,13 @@ def bulk_item_insert(
             A string indicating the number of items successfully added.
         """
         request = kwargs.get("request")
+
+        if os.getenv("ENABLE_DATETIME_INDEX_FILTERING"):
+            raise HTTPException(
+                status_code=400,
+                detail="The /collections/{collection_id}/bulk_items endpoint is invalid when ENABLE_DATETIME_INDEX_FILTERING is set to true. Try using the /collections/{collection_id}/items endpoint.",
+            )
+
         if request:
             base_url = str(request.base_url)
         else: