fix: Require signatures for ssl_check request verification

[homanp]

Summary

• stop RequestVerification from skipping HMAC validation solely because a form body contains ssl_check=1
• keep the existing Socket Mode verification skip
• add regression coverage for sync, async, and WSGI dispatch paths

Why

When ssl_check_enabled=False, the SSL-check middleware does not intercept ssl_check=1 requests. Request verification still needs to authenticate those HTTP requests before they can reach normal middleware or slash command listeners.

Fixes #1494.

Testing

• ./scripts/run_tests.sh "tests/slack_bolt/middleware/request_verification/test_request_verification.py tests/slack_bolt_async/middleware/request_verification/test_request_verification.py tests/scenario_tests/test_slash_command.py tests/scenario_tests_async/test_slash_command.py tests/adapter_tests/wsgi/test_wsgi_http.py"
• ./scripts/lint.sh --no-install
• ./scripts/run_mypy.sh --no-install

[salesforce-cla]

Thanks for the contribution! Before we can merge this, we need @homanp to sign the Salesforce Inc. Contributor License Agreement.

[homanp]

CLA was signed but not showing up here.

[homanp]

@WilliamBergamin found this as well, not sure if this was "by-design" or not but worth taking a look.

[WilliamBergamin]

This is another awesome find 💯 🚀

Reproducing this locally and testing it out took me longer then I want to admit, but changes look good to me 🥇 thanks for adding these unit tests, they will prevent us form introducing similar behavior in the future

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.32%. Comparing base (ae0ba57) to head (a54bf56).
⚠️ Report is 3 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1495   +/-   ##
=======================================
  Coverage   91.32%   91.32%           
=======================================
  Files         228      228           
  Lines        7262     7262           
=======================================
  Hits         6632     6632           
  Misses        630      630           

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[WilliamBergamin]

This might of been by design to allows users that disable SslCheck middleware to somehow handle these requests manually through a handler 🤔 this feel like a super edge case that leaves the door wide open

User that want to handle their own ssl check logic are able to do so in a global middleware