fix: improve the robustness of the payload extract logic

[WilliamBergamin]

Summary

These changes aim to improve the robustness of the payload extraction logic!

#1447 highlights that in some edge cases our payload extraction logic will fail and raise a TypeError before the RequestVerification middleware can execute.

The ideal solution to this issue is to move the context building from the request initialization to a middleware that runs immediately after RequestVerification middleware. But this would constitute a breaking change.

This PR aims to introduce none breaking changes that make the context building more robust and prevents errors from raising before RequestVerification middleware executes.

Testing

Unit tests should be sufficient, but feel free to spin up an app tests some edge cases

Category

• slack_bolt.App and/or its core components
• slack_bolt.async_app.AsyncApp and/or its core components
• Adapters in slack_bolt.adapter
• Document pages under /docs
• Others

Requirements

Please read the Contributing guidelines and Code of Conduct before creating this issue or pull request. By submitting, you are agreeing to those rules.

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've run ./scripts/install_all_and_run_tests.sh after making the changes.

[codecov]

Codecov Report

❌ Patch coverage is 95.23810% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 91.47%. Comparing base (f1bc61f) to head (4f2a1fd).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
slack_bolt/request/internals.py	95.23%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1464      +/-   ##
==========================================
+ Coverage   91.43%   91.47%   +0.04%     
==========================================
  Files         232      232              
  Lines        7334     7334              
==========================================
+ Hits         6706     6709       +3     
+ Misses        628      625       -3     

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[zimeg]

@WilliamBergamin Super nice fix with minimal changes! 🌟

I'm also curious to improving the middleware sequences but let's keep discussing this ongoing. It's a promising pattern I think!

[zimeg]

🧪 praise: These are solid test cases!

🔬 suggestion(non-blocking): Would assertions also that these values are None be useful?

[WilliamBergamin]

Yess I would of liked to get some asserts in there but some of these payloads are actually valid and won't result in null, the goal of the test it to make sure we don't raise an errors

I hope the comment is sufficient 🙏 we can always improve the test in a follow up PR 🚀