feat: maximum_concurrency option in on_sqs_message

[adityamohta]

Issue #2031

Description of changes:

This PR adds option to configure MaximumConcurrency value for sqs event source lambdas.

The option can be used like following:

@app.on_sqs_message(queue='my-queue', batch_size=1, maximum_concurrency=20)
def handle_sqs_message(event):
    ...

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[leobarcellos]

This is really useful.

[adityamohta]

The test failure for python3.8 in ci seem unrelated to this PR.

[jamesls]

Thanks for the pull request.

Yeah those py38 errors should be fixed in #2092, so rebasing from master should fix this. I can take a look at this tomorrow.

[adityamohta]

Yeah those py38 errors should be fixed in #2092, so rebasing from master should fix this. I can take a look at this tomorrow.

Ah, makes sense, thanks for sharing that @jamesls ! 🙇🏻‍♂️