[8.17] (backport #8359) updatecli: create PRs per active branch and refactor slack notifications

[mergify]

What does this PR do?

• Run on Saturdays, a few hours after VM images are produced.
• Create PRs per active branch instead of using the backport labels.
• Use slack composite action.
• Notify the robots team if something goes wrong with the GH actions.
• Enable auto approval and auto-merge with Mergify [Need to configure the branch protections accordingly]

Why is it important?

A follow-up from #8211

Checklist

• I have read and understood the pull request guidelines of this project.
• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in ./changelog/fragments using the changelog tool
• I have added an integration test or an E2E test

Disruptive User Impact

How to test this PR locally

$ GITHUB_TOKEN=$(gh auth token) \
  GITHUB_ACTOR=v1v \
  BRANCH_NAME=main updatecli apply \
    --config .ci/updatecli/updatecli-bump-vm-images.yml \
    --values .ci/updatecli/values.d/scm.yml

Produced v1v#7

Then I targeted a different branch

$ GITHUB_TOKEN=$(gh auth token) \
  GITHUB_ACTOR=v1v \
  BRANCH_NAME=main updatecli apply \
    --config .ci/updatecli/updatecli-bump-vm-images.yml \
    --values .ci/updatecli/values.d/scm.yml

Produced v1v#8

Related issues

Questions to ask yourself

• How are we going to support this in production?
• How are we going to measure its adoption?
• How are we going to debug this?
• What are the metrics I should take care of?
• ...

---

This is an automatic backport of pull request #8359 done by [Mergify](https://mergify.com).

[v1v]

I somehow thought that buildkite/elastic-agent would run and do nothing if changes are in the list of changes to skip the CI.

However, it's still pending

For instance, I've seen it work fine for #8312:

Now, what's the reason buildkite/elastic-agent - No changes required CI. Skipped. was not actually skipped but pending in this PR?

[mergify]

This pull request has not been merged yet. Could you please review and merge it @v1v? 🙏

[mergify]

This pull request has not been merged yet. Could you please review and merge it @v1v? 🙏

[dliappis]

LGTM

[dliappis]

@v1v re your previous comment, after clicking update branch, there was a rerun which now shows the green tick box in buildkite/elastic-agent (mentioning No changes required in CI. Skipped):

Even though it's a green tick box, it seems it's not sufficient for automerge and the requirement for buildkite/elastic-agent isn't met.
I've noticed you've merged other backports of the same PR manually e.g. #8507

Is this something we'll always need to do going forwards?

[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b mergify/bp/8.17/pr-8359 upstream/mergify/bp/8.17/pr-8359
git merge upstream/8.17
git push upstream mergify/bp/8.17/pr-8359

[dliappis]

LGTM fixed a merge conflict after 0cff839

[v1v]

Is this something we'll always need to do going forwards?

I'm still figuring out what the path forward is - when I enabled the mergify auto-merge, I think there was some condition that worked as expected:

• [main][Automation] Bump stack images versions to 9.1.0-3043fce3 #8543 (comment)

That mistakenly made me think things were good to move forward.