PHPC depends on mongoc_bulk_operation_new(), as it allows a bulk operation to be created independently of a client. Currently, mongoc_bulk_operation_t is only associated with an explicit session ID through mongoc_collection_create_bulk_operation_with_opts(), which PHPC cannot use, since the collection is only known at execution time. A mongoc_bulk_operation_set_client_session() setter would allow us to assign the session to a bulk write at execution time, as we currently do for client, database, collection, hint, and write concern.