fix: require a custom 'api' url to send to instead of absolute urls as a 'method'

[zimeg]

Summary

This PR requires using a custom api URL in step inputs to send to URLs that are not "https://slack.com/api/".

Fixes unexpected behaviors noted in slackapi/node-slack-sdk#2176 for steps using a variable method for cases of composite action workflows or of variable inputs from outputs of a different step.

No change to functionalities when using as a standalone step!

Preview

The format shown in the README.md is now required to send to a custom api URL:

  - name: Post text to a Slack channel
    uses: slackapi/slack-github-action
    with:
-     method: http://localhost:8080/chat.postMessage
+     api: http://localhost:8080/
+     method: chat.postMessage
      token: ${{ secrets.SLACK_BOT_TOKEN }}
      payload: |
        channel: ${{ secrets.SLACK_CHANNEL_ID }}
        text: "howdy <@channel>!"

Requirements

• 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.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.85%. Comparing base (e7edf37) to head (ced6b72).
Report is 7 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #420   +/-   ##
=======================================
  Coverage   99.85%   99.85%           
=======================================
  Files           7        7           
  Lines         702      703    +1     
=======================================
+ Hits          701      702    +1     
  Misses          1        1           

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[WilliamBergamin]

This seems good to me 💯

But any chance we could add a unit test that ensures the override configuration sends a request to the correct uri?
I looked through the test but did not find such a test, but maybe I missed it

[mwbrooks]

Good call @WilliamBergamin - I agree, a test would be great. Otherwise, looks good! 👌🏻

[zimeg]

@WilliamBergamin @mwbrooks Thank y'all both for the reviews 🙏

These tests were stumping me for a bit longer than I'd like to admit but related work in an adjacent repo brought some great inspiration 😉

But any chance we could add a unit test that ensures the override configuration sends a request to the correct uri?

This doesn't seem simple without catching actual HTTP requests, but we now test that the expected arguments are used in both the WebClient constructor and .apiCall method.

For now I'm hoping this is alright with the upstream tests we also have:

https://github.com/slackapi/node-slack-sdk/blob/29c1e1aff222a8c40513c55e874c5a9149131f40/packages/web-api/src/WebClient.spec.ts#L534-L546

[WilliamBergamin]

Nice work 💯