In our implementation of collection::bulk_write, we're currently not using the collection's write concern due to the call to libmongoc::bulk_operation_set_collection getting a new mongoc_collection_t from the client rather than using the existing one with the options set. To remedy this, we should replace the call to libmongoc::bulk_operation_new in the constructor for bulk_write with a call to libmongoc::collection_create_bulk_operation, which properly handles inheriting the write concern from the collection.