Automerge PR workflow v2

[CAMOBAP]

Background

We already had this task in the past https://github.com/metanorma/ci/issues/45 after resolving issues it worked at some point.

But for the last update, it stop working for instance this PR https://github.com/metanorma/metanorma-model-standoc/pull/39

Action items

• [x] investigate why it breaks
• [x] review again approaches to implement automerge
• [ ] implement approach

Conditions:

• all checks are passed
• PR is not in draft state

[CAMOBAP]

Per https://github.com/pascalgn/automerge-action

The action will only wait for status checks that are marked as required in the branch protection rules

So probably our checks aren't required can be checked with API call https://docs.github.com/en/rest/checks/suites?apiVersion=2022-11-28#list-check-suites-for-a-git-reference

Also we can request them explicitly in the commit message request-checks: true as described here https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/collaborating-on-repositories-with-code-quality-features/about-status-checks

[CAMOBAP]

commit message request-checks: true doesn't work

[CAMOBAP]

https://github.com/pascalgn/automerge-action/issues/234 - looks like exact description of the problem, to be implemented as in second comment