Update open merge requests when project approval rules change

Problem to solve

As noted in the docs: Any merge requests that were created before changing the rules will not be changed. They will keep the original approval rules, unless manually overridden.

We are likely not applying approval rule updates to open merge requests currently due to performance reasons, but it may be the users expectation (pending workflowsolution validation) that updating the projects approval rules or changing the branch for the approval rules will affect existing merge requests.

Proposal

When updating the approval rules in the project settings, these changes should apply to existing merge requests that have not had their approval rules overridden.