Ability to tag default reviewers as mandatory or optional

In Bitbucket 4.9 we will have the ability to create default reviewers for a project. Default reviews provide the ability to specify reviews required, but do not distinguish between reviewer types.

As teams grow, we would like to increase the number of default reviewers to include new members so they are privy to recently published code. New team member should be considered optional as often they don't have the depth of understanding needed for the review and are included for learning purposes.

Reviews required should only be applied to mandatory reviewers that are specified for the project

This implies either James or Jon must complete their review for the pull request to be approved