Support merge queue branch protections

[ehuss]

This is an issue to track adding merge queue branch protection support. This is currently not possible because it is not supported by GitHub's API. I figured it might be helpful to have an issue to track it nonetheless.

There are open requests for this at:

• https://github.com/orgs/community/discussions/50893
• https://github.com/orgs/community/discussions/77614

AFAIK, it should be OK for admins to manually set this even if the repo is managed in the team database. It looks like update_branch_protection should be compatible. I have not tested this, yet, since all merge-queue repos I know of aren't tracked, yet.

[ehuss]

Noting the last update from GitHub: https://github.blog/changelog/2024-02-27-repository-rules-configure-merge-queue-rule-public-beta/#limitations

They mention API support being "near future". I don't know if that means for rulesets or branch protections. I have the feeling that GitHub is pushing people towards rulesets and away from branch protections, so I'm not sure if they will both be fully supported.

[ehuss]

Update: https://github.blog/changelog/2024-07-31-repository-updates-july-31st-2024/#repository-rules-updates

Merge queues + rulesets are now stabilized, and available via the GraphQL API. I continue to believe that GitHub will not be backporting new features to branch protections. Updating sync-team to use rulesets is probably not easy, though.