add trailing slash to the end of the url

[HTSagara]

Summary

This PR addresses issue #1541 by ensuring that a trailing / is appended to the end of the URL in base_url if it is not already provided. This change ensures consistent URL formatting and avoids potential issues caused by missing trailing slashes in API calls.

Testing

1. Unit Tests
   Run the following command to ensure all relevant test cases pass:

./scripts/run_unit_tests.sh tests/slack_sdk/web/test_web_client.py

2. Manual Testing

• Use a custom base_url without a trailing / in a sample implementation. Confirm that the URL is automatically appended with a / during API calls.
• Use a base_url with a trailing / and verify that no additional / is appended.

Category

• [x ] slack_sdk.web.WebClient (sync/async) (Web API client)
• slack_sdk.webhook.WebhookClient (sync/async) (Incoming Webhook, response_url sender)
• slack_sdk.socket_mode (Socket Mode client)
• slack_sdk.signature (Request Signature Verifier)
• slack_sdk.oauth (OAuth Flow Utilities)
• slack_sdk.models (UI component builders)
• slack_sdk.scim (SCIM API client)
• slack_sdk.audit_logs (Audit Logs API client)
• slack_sdk.rtm_v2 (RTM client)
• /docs (Documents)
• /tutorial (PythOnBoardingBot tutorial)
• tests/integration_tests (Automated tests for this library)

Requirements

• [x ] I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• [x ] I've read and agree to the Code of Conduct.
• [x ] I've run python3 -m venv .venv && source .venv/bin/activate && ./scripts/run_validation.sh after making the changes.

[seratch]

Thanks for taking the time to make this PR! Can you apply the same change to legacy_base_client.py for consistency?

[seratch]

LGTM; I will be offline for a while but other maintainers will merge this once the CI builds pass. Thank you for taking the time to fix this issue!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.89%. Comparing base (d1dffb7) to head (b491388).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1594      +/-   ##
==========================================
- Coverage   84.91%   84.89%   -0.03%     
==========================================
  Files         113      113              
  Lines       12622    12628       +6     
==========================================
+ Hits        10718    10720       +2     
- Misses       1904     1908       +4     

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[WilliamBergamin]

lgtm, thank you 💯

[HTSagara]

Thank you for all the support 🙏

[HTSagara]

Hi @WilliamBergamin and @seratch I noticed that after I changed the legacy_base_client.py it caused an error by adding a (//) in the api_url when concatenating the base_url with the api_method.

I just submitted the issue with the PR #1596 in order to fix it.

Apologies for the mistake.

[WilliamBergamin]

No worries 🤔 I had a feeling these changes may affect more edge cases then we could think of

My concern is that our unit tests did not catch this edge case and may have missed others that we are unaware of, It may be simpler to revert this commit, add more tests around this area in a separate PR and reopen these changes with updates to the tests