enable improved pricing model based on actual usage
Description
Current EE pricing can get out of control for very large organizations that allow everyone to signup for GitLab accounts. A better approach would be usage based pricing.
Proposal
If a company purchased 100 licenses, only count users that interacted with GitLab over last month against license total. If one month's total user count exceeds licensed amount at annual renewal they pay for 1/2 annual license cost for additional users over license limit (e.g. August has 300 users, most users of any month that year so they pay $39100 for additional users at renewal + $39300 for upcoming year).
This helps companies by not forcing them to constantly research who is/isn't using GitLab and block them to avoid unnecessary license costs. Helps GitLab because it will likely result in less concern with switch to EE and encouraging as much usage as possible (because they know they won't be charged much for a user who only tries it once).
If taking a look at maximum users by month isn't something you want to consider even only charging for users that actually used GitLab over the 12 month period would be helpful.
Links / references
Related to https://gitlab.com/gitlab-org/gitlab-ce/issues/12925, https://gitlab.com/gitlab-org/gitlab-ce/issues/3962, https://gitlab.com/gitlab-org/gitlab-ee/issues/1022. Make https://gitlab.com/gitlab-org/gitlab-ce/issues/11844 less important for EE customers.