Trainee maintainers count as reviewers, but should get more reviews than
most reviewers, as they need practice to become a maintainer. This makes
them three times as likely to be picked (compared to another reviewer;
compared to before, it's roughly twice as likely at the current numbers
for each).
Also, switch to `Array#sample` because I think it looks nicer.
This extends Danger so it informs MR authors that single codebase merge
requests need to be approved by a specific group of engineers.
Co-authored-by: Yorick Peterse <yorickpeterse@gmail.com>
Make danger pick reviewers and maintainers at random, for feontend,
backend, database, etc, changes, whenever files belonging to those
teams get changed.
