We want to set up a pool code review system where any developer can see a list of all pending code review requests and pick some to review. We're using Visual Studio Team Services.
As a first step, I need to allow the entire Project Collection Valid Users group to be added as reviewer of a pull request. (Currently the field seems to accept only users who are explicit members of the project team.) The second step is to grant read-access to all projects to all collection valid users.
The latter step seems to be answered by this answer.
But I'm completely stuck on making everyone a pull request reviewer. Is this even possible? If so how? (I'd prefer not to rely on a third-party extension if it can be done without.)