fix: add descriptive error message to SendBatchOperationFailedException

[Baqirrizvidev]

This PR addresses Issue #1605 by constructing a detailed, descriptive exception message when creating a SendBatchOperationFailedException.

Problem

Previously, in AbstractMessagingTemplate.handleFailedSendBatch, a SendBatchOperationFailedException was created with a hardcoded empty string "" as the exception message. As a result, e.getMessage() returned "", rendering the exception silent in logs and requiring developers to manually extract details via e.getSendBatchResult().failed().

Solution

This PR updates AbstractMessagingTemplate to dynamically construct a diagnostic error message when a batch send operation fails. The message now contains:

• The target SQS queue/endpoint.
• The raw SQS message ID (or Spring message ID) of each failed message in the batch.
• The associated failure error message returned from the SQS client.

Testing

• Added assertions to the existing shouldThrowIfHasFailedMessagesInBatchByDefault unit test in SqsTemplateTests to verify that SendBatchOperationFailedException contains a message with the expected queue name, failed message ID, and SQS error details.
• Verified that all unit tests pass successfully.

[tomazfernandes]

@Baqirrizvidev thanks for the PR.

Left a comment for a null guard to be on the safe side. We're changing correlation in a few places. Should be good to merge with that change.

[tomazfernandes]

Let's add a small guard against null here in case correlation fails in a previous step and the message is not included in the batch:

E.g.:

failed.message() != null ? MessageHeaderUtils.getRawMessageId(failed.message())                                                                                                                                                                                   
                                                                        : "unknown"