Fix #1204 Deprecation Warnings in Slack Bolt Integration with Sanic

[HTSagara]

This Pull Request addresses #1204 deprecation warnings and type-related errors that occur when integrating Slack Bolt with Sanic. The warnings were caused by the use of Sanic's outdated dict-based cookie handling syntax, which has been deprecated since Sanic v23.3. These issues surfaced during testing and when handling requests.
Key Changes:

**Updated Cookie Handling: **

• Replaced the old dict-style cookie setting syntax with Sanic's recommended add_cookie method.
• Ensured proper type handling for cookie attributes such as path, domain, expires, and max-age.

Resolved Type Errors:

• Explicitly converted path and domain attributes to strings or assigned appropriate defaults.
• Handled expires and max-age fields gracefully to align with Sanic's requirements.

Testing:

• The changes have been validated through existing test cases

Category (place an x in each of the [ ])

• 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 (place an x in each [ ])

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 90.96%. Comparing base (4eb3855) to head (d47a5e7).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1220      +/-   ##
==========================================
+ Coverage   90.94%   90.96%   +0.02%     
==========================================
  Files         222      222              
  Lines        7506     7501       -5     
==========================================
- Hits         6826     6823       -3     
+ Misses        680      678       -2     

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[hello-ashleyintech]

@HTSagara Thanks for submitting this PR! 🙌 I see that your base branch is out of date with main, would you be able to merge the latest main into this branch and push it up?

[HTSagara]

@hello-ashleyintech thank you for the feedback. I just updated my branch with the main

[seratch]

@HTSagara Thank you so much for taking the time to make these changes! I've added a few additional changes (= removed the comments repeating what the code does, added assertions in the Sanic unit tests to verify the cookie data behavior) and merged your changes as a single commit: 35a4b09

Thanks again for your contribution! 🎉