Create `StreamsEventResponse`

[ryo-murai]

I'm writing a lambda function receiving DynamoDB stream events. It replies a StreamsEventResponse to report failed items in partial error case, so that the AWS re-delivers only the failed event items. I would appreciate if that response type is provided.

Document for the StreamsEventResponse is below: https://docs.aws.amazon.com/lambda/latest/dg/with-ddb.html#streams-batchfailurereporting-syntax

At least, the following keys are required to work reporting the item failures.

{ 
  "batchItemFailures": [ 
        {
            "itemIdentifier": "<id str>"
        }
    ]
}