docs: document custom step usage

[WilliamBergamin]

This PR aims to provide documentation for custom step usage in the bolt framework

Testing

1. Pull this branch
2. cd ./docs
3. npm install
4. npm start
5. http://localhost:3000/bolt-python/concepts/custom-steps

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.

[WilliamBergamin]

I will need some help for the translation 🙏

[filmaj]

LGTM, my only suggestion would be to link to api.slack.com docs around custom steps for bolt usage in the introductory sentence(s), linking to Haley's work recently where possible.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.80%. Comparing base (fbd6462) to head (52287be).

Additional details and impacted files

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  Coverage   91.80%   91.80%           
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  Files         186      186           
  Lines        6408     6408           
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  Misses        525      525           

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[zimeg]

Super solid lift here, thank you tons! 💪 🥇 🎉

Sharing similar suggestions as in slackapi/bolt-js#2198 that I think are worth considering before merging, and I think some of the updates @filmaj suggested to the "interactivity" section in that PR would be nice to include here too!

[zimeg]

Suggested change

	def sample_step_callback(inputs: dict, ack: Ack, fail: Fail, complete: Complete):
	try:
	ack()
	def sample_step_callback(inputs: dict, fail: Fail, complete: Complete):
	try:

Calling ack seems to be valid here but I don't think it's necessary 🤔 Please correct me if this is wrong though!

[WilliamBergamin]

I prefer to keep it in the docs, there are a number of issues opened related to calling ack before executing custom logic

Keeping it in hopes that it will help developers avoid a bug 🙏

[zimeg]

Suggested change

	Your app can use the `function()` method to listen to incoming [custom step requests](https://api.slack.com/automation/functions/custom-bolt). Custom steps are used in Workflow Builder to build workflows. The method requires a step `callback_id` of type `str`. This `callback_id` must also be defined in your [Function](https://api.slack.com/concepts/manifests#functions) definition. Custom steps must be finalized using the `complete()` or `fail()` listener arguments to notify Slack that your app has processed the request.
	Your app can use the `function()` listener to listen to incoming [custom step requests](https://api.slack.com/automation/functions/custom-bolt).
	Adding a custom step starts with a definition in [the app manifest](https://api.slack.com/concepts/manifests#functions) and a `function()` listener listening for the `callback_id` of that function. Upon function execution the listener is called and can run whatever code, but must finish with either the `complete()` or `fail()` listener argument to end the step:

Same suggestion as slackapi/bolt-js#2198 (comment)

[WilliamBergamin]

The rest of the documentation uses the method terminology instead of the listener

I think its better to be consistent and stick to method

We can send a follow up PR to update all the terms 👍