fix awsRegion field in S3 notification

[bentsku]

Motivation

It had been shown in the multi-account tests that we've had an issue where the awsRegion was not correct. It was using the client request region, when it should have been the bucket region.

Also, per the documentation for events: https://docs.aws.amazon.com/AmazonS3/latest/userguide/ev-events.html, the region field for the event should be the bucket region, which means the events client needs to be created with the bucket region and not the client region, as the region field in the event is from the internal client.

Also validated the behaviour with AWS, that the region was of the bucket and not the client.

Changes

Fix the event payload for SQS/SNS/Lambda to use the region of the bucket for the awsRegion field.
Fix the region for the events client used in the notifier.

Add 2 tests to validate AWS behaviour (one created a bucket in another region than the default client for SQS, and one creating a client in a secondary region and the bucket in the default one).

[github-actions]

LocalStack Community integration with Pro

       2 files         2 suites   1h 9m 12s ⏱️
2 258 tests 1 754 ✔️ 504 💤 0 ❌
2 259 runs  1 754 ✔️ 505 💤 0 ❌

Results for commit 3bd070d.

♻️ This comment has been updated with latest results.

[coveralls]

coverage: 82.993% (-0.003%) from 82.996% when pulling 3bd070d on fix-s3-notification-region into 6662d91 on master.

[macnev2013]

Thanks for the PR 🚀 LGTM