def add(user_name, repo_name, reviewer_username, params={})
      update_and_validate_user_repo_params(user_name, repo_name)
      normalize! params

      put_request("/2.0/repositories/#{user_name}/#{repo_name}/default-reviewers/#{reviewer_username}", params)
    end
def add(user_name, repo_name, reviewer_username, params={})
      update_and_validate_user_repo_params(user_name, repo_name)
      normalize! params

      put_request("/2.0/repositories/#{user_name}/#{repo_name}/default-reviewers/#{reviewer_username}", params)
    end
Add a user to the default-reviewers list for the repo

 = Examples
  bitbucket = BitBucket.new
  bitbucket.repos.default_reviewers.add 'user-name', 'repo-name', 'reviewer-username'