fix(event_handlers): handle lack of headers when using auto-compression feature

[tbuatois]

Issue number: #1327

Summary

This PR add the ability use compress=True in decorator without throwing an error for a request containing null headers

Changes

• Add check for NoneType / null header in get_header_value function and return default if so
• Add corresponding unit test test_compress_no_accept_encoding_null_headers

User experience

• Before
  Error for a request with empty/null headers to a method with compress=True:
  'NoneType' object has no attribute 'items'", "errorType": "AttributeError"

That was due to an error from api_gateway.py at line 212:

 if self.route.compress and "gzip" in (event.get_header_value("accept-encoding", "") or ""):

• After

No more error, return default value as expected.

Checklist

If your change doesn't seem to apply, please leave them unchecked.

• Meet tenets criteria
• I have performed a self-review of this change
• Changes have been tested
• Changes are documented
• [x ] PR title follows conventional commit semantics

Is this a breaking change?

RFC issue number:

Checklist:

• Migration process documented
• Implement warnings (if it can live side by side)

Acknowledgment

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

Disclaimer: We value your time and bandwidth. As such, any pull requests created on non-triaged issues might not be successful.

[boring-cyborg]

Thanks a lot for your first contribution! Please check out our contributing guidelines and don't hesitate to ask whatever you need.

[github-actions]

No related issues found. Please ensure there is an open issue related to this change to avoid significant delays or closure.

[codecov-commenter]

Codecov Report

Merging #1325 (281722d) into develop (ab23491) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop    #1325   +/-   ##
========================================
  Coverage    99.88%   99.88%           
========================================
  Files          119      119           
  Lines         5427     5429    +2     
  Branches       619      620    +1     
========================================
+ Hits          5421     5423    +2     
  Misses           2        2           
  Partials         4        4           

Impacted Files	Coverage Δ
...lambda_powertools/utilities/data_classes/common.py	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 4bbcc24...281722d. Read the comment docs.

[heitorlessa]

tiny change to address another potential error

[boring-cyborg]

Awesome work, congrats on your first merged pull request and thank you for helping improve everyone's experience!