Add GitLab licensing and subscription terminology to AI glossary
What does this MR do?
Adds clear definitions for GitLab licensing and subscription terminology to the AI glossary based on internal discussion about terminology confusion.
Added terms:
- Add-on: Defines Duo Core/Pro/Enterprise, compute minutes, and storage
- User add-on assignment: Explains how add-ons are assigned to users, with special note about Duo Core being namespace-level
- License: Clarifies this specifically refers to license files for Self-Managed instances
- Subscription: Explains the tier system (Free/Premium/Ultimate) and differences between SaaS and Self-managed
Why was this change made?
As noted in the related issue, terminology confusion between fulfillment and other teams can cause unnecessary confusion. This adds clear, authoritative definitions to help everyone use consistent terminology.
Related issues
Relates to #578254 (closed)