numberOfReviewers is misleading when useReviewGroups is enabled

[paniko0]

Assuming the following configuration, I'd expect that only one reviewer would be selected given that numberOfReviwers is set to 1, instead, it returns 3 values: user1, user2, and a user in the charlie group.

addReviewers: true

numberOfReviewers: 1

useReviewGroups: true

reviewGroups:
  alpha:
    - user1
  bravo:
    - user2
  charlie:
    - user3
    - user4
    - user5

I believe either the name of the configuration numberOfReviwers is misleading when useReviewGroups is enabled, or there's a bug where it assigns more than one reviewer to the PR.

I can work on a PR to fix the problem, I just need to know which approach you guys think it's the best. Personally, I think numberOfReviewers should always be respected regardless of the number of developers each group has. I'd also include a configuration to the group, so it can select one or multiple developers per group to be used later by the numberOfReviewers variable.