[SPIKE] Investigate implementation of branch protections which respect conditional build gates

Background

Right now, it is possible to merge a PR if you receive approval, but before all build steps are passed. This has led to issues where PRs have been merged with failed builds. It also prevents us from enforcing that all branches are up to date before merge (this has also led to problems due to conflicts between PRs merged around the same time).

An attempt to implement branch protections proved unsuccessful since we use conditional github actions in the repo. For example, if you enforce that unit tests pass, but you only make a documentation change, Github will sit waiting for unit tests which never get triggered since no .go file is modified. This prevented PRs from being merged.

Task

Investigate if there is some mechanism in Github to only block on a build gate if it's actually run.

No files, tests, or entry points are named. Start by reviewing the repository’s conditional GitHub Actions and current branch protection settings, then check GitHub’s documentation for protections that handle conditionally skipped build gates. Done means documenting a viable mechanism or confirming the limitation and outlining the required approach.