Don't charge for guests in GitLab.com Gold groups
Problem to solve
In #5693 (closed), guests don't count against the Ultimate license limit. We should add this to Gold plans on GitLab.com as well; when Guests are added to a GitLab.com group that has subscribed to Gold, we should not bill for these users.
We potentially bill for newly added users to a GitLab.com group. Guests shouldn't trigger an additional charge for Gold groups.
What does success look like, and how can we measure that?
No additional charges for GitLab.com guests in Gold plans.