Add Slack operators how-to guide

[kevin1kevin1k]

• Solve Add how-to Guide for Slack operators #11919
• Generate a how-to guide for Slack operators (currently only SlackAPIFileOperator; could add SlackAPIPostOperator later)
• Fix and unify the code sample in API page

[potiuk]

Looks good. Let me close and reopen to rebuild

[github-actions]

The PR is likely OK to be merged with just subset of tests for default Python and Database versions without running the full matrix of tests, because it does not modify the core of Airflow. If the committers decide that the full tests matrix is needed, they will add the label 'full tests needed'. Then you should rebase to the latest main or amend the last commit of the PR, and push it with --force-with-lease.

[potiuk]

Would be cool to have 4 PRS merged after the workshops !

[kevin1kevin1k]

Thanks again, really enjoyed the sprint today!

[potiuk]

Cool - one thing to fix - we are building an inventory of howto guides so you need to add it to ariflow/providers/slack/provider.yaml (see other providers for an example).

[kevin1kevin1k]

No problem, hopefully the new commit would fix that :)

[potiuk]

Cool @kevin1kevin1k ! Thanks for the participation in the workshop!