feat: Project Update API to wait for call to the Core

[jachro]

This PR modifies the Project Update API in a way that the call to update project metadata in the Core is not done asynchronously but synchronously. With the change, eventual problems on the Core side will be reported to the caller.

Another change regards projects with protected branches that Core cannot push to. In such cases, Project Update API returns Conflict 409 status and updates only GL and TS but only with values that don't have to be passed to the Core. The values that need calling the Core are pushed by the Core to a new branch about the user is informed and for which the user needs to create a PR and merge it. An example response in this case will be:

{
  "message": {
    "details": "Only visibility=public got updated in the TS due to branch protection rules on the default branch 'main'. However, an update commit was pushed to a new branch 'main/344422' which has to be merged to the default branch with a PR",
    "branch": "main/344422"
  }
}