chore: create /add-sub-issue and /remove-sub-issue commands

[andyatmiami]

related: #325

This new GitHub Actions workflow listens for issue comments and processes commands to add or remove sub-issues using the Javascript client. It includes error handling and posts feedback to the issue for auditability as well as if any errors occur during execution.

Acceptable input formats (and multiple space-delimited arguments can be provided):

/add-sub-issue #1
/add-sub-issue 1
/add-sub-issue https://github.com/kubeflow/notebooks/issues/1

Additionally, the entirety of a comment is scanned/parsed by the GHA - so the following is also valid:

we need these!

/add-sub-issue #1 #2

and we don't need these

/remove-sub-issue #3 #4

• this would add issues 1 and 2 and remove issues 3 and 4 from the "parent" issue on which the comment was added.

ℹ️ Be mindful of underlying constraints enforced in GH regarding sub-issues:

• An issue can only be a sub-issue to 0 or 1 issues
• Trying to add an issue as a sub-issue when it is already assigned as a sub-issue results in error

Also, in this commit, the ability to assign sub-issues is open to a set of users defined in the workflow yaml as a JSON string array within the job-level if conditional. The current collection identifies all epic owners and technical leaders for Notebooks 2.0.

Please note the workflow YAML file has been named generically to potentially house other "slash commands" in the future although the current implementation is only focused on /add-sub-issue and /remove-sub-issue.

To "see" the code in action and test it out - you can see this issue here on a personal repo of mine I was using to test/construct the code:

• [EPIC] A andyatmiami/github-actions-playground#1

[paulovmr]

/ok-to-test

[caponetto]

It seems hard to maintain this code as a giant string.
Can we move the code to an external JS file under, possibly, .github/scripts folder and call it here?
At least, we'd have a few IDE capabilities.

[andyatmiami]

I'd prefer to get @thesuperzapper to weigh in on his preferences here... I don't really see the external files pattern used elsewhere in kubeflow repositories - and don't really want to deviate unless we get an established community member to speak in favor of the change.

I totally appreciate and understand the motivation behind the ask, however!

[thesuperzapper]

I think it's fine to leave this inline, as the script is specific to the context of actions/github-script@v7 and there is only one usage of this in the kubeflow org (and even notebooks project) right now.

[thesuperzapper]

Thanks, hopefully this solves the problem with permissions to add sub-issues.

/lgtm
/approve

[google-oss-prow]

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