feat: add has_been_called on complete & fail utility

[WilliamBergamin]

Summary

These changes allow to easily determine if fail or complete was invoked, invoking both in the same handler can sometimes lead to errors returned from the Slack API

Testing

try:
    # do some things to create the step output
    
    complete(outputs={"search_result": invalid_object}) # this could cause a parameter validation error from the Slack API
except Exception as e:
    logger.error("Unexpected error occurred")
    if not complete.has_been_called():
        fail(error="internal error")

The same applies to the fail utility function 🙏

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

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.05%. Comparing base (1d4e86b) to head (c970416).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1390      +/-   ##
==========================================
+ Coverage   91.03%   91.05%   +0.02%     
==========================================
  Files         222      222              
  Lines        7514     7534      +20     
==========================================
+ Hits         6840     6860      +20     
  Misses        674      674              

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[cchensh]

LGTM

[zimeg]

@WilliamBergamin LGTM! This is quite slick I admit 🚢 💨