fix: SQS Delete Batch ID's should be distinct, which MessageID is not guaranteed to be

[flipscholtz]

When deleting a batch of SQS messages, the Batch ID's have to be unique.
If not, a 'BatchEntryIdsNotDistinct' error is returned and none of the messages are deleted.

Setting this ID equal to the MessageID causes problems because multiple receipts of the same message will have the same MessageID, although it's not the same ReceiptHandle.
For e.g. a single batch may contain:
messageA#receipt1
messageA#receipt2 .
In both cases, the MessageID is messageA but in terms of batched deletion it's two different items.

According to the docs here, the ID passed to DeleteBatch is just a correlation ID, so it can be set to anything user-generated:

Note
The Id s of a batch request need to be unique within a request.

This identifier can have up to 80 characters. The following characters are accepted: alphanumeric characters, hyphens(-), and underscores (_).

So we can just set it to a random UUID to avoid duplicates.