OAuth 2.1 server had a single pricing statement anywhere, and it said
the feature is free during beta. This states the actual model everywhere
the feature is documented or sold: there is no separate charge, and
users who sign in through the OAuth server count toward Auth MAUs.
- docs getting started: replace the "free during beta" sentence with the
MAU-based pricing statement
- docs overview: add a Pricing section linking to the MAU usage guide
and the pricing page
- docs MCP authentication: note that agents authenticate as existing
users, and MAUs count per distinct user, so multiple agents for one user
count once
- www pricing comparison table: add an "OAuth 2.1 Server" row (included
on all plans) with a tooltip, and extend the MAU tooltip to cover OAuth
server sign-ins
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## Summary by CodeRabbit
* **Documentation**
* Clarified that OAuth 2.1 Server is available on all plans without a
separate charge.
* Explained that OAuth sign-ins count toward Monthly Active Users
(MAUs), with multiple agents for one user counted once.
* Added links to MAU and pricing guidance.
* **Pricing**
* Added OAuth 2.1 Server as a plan feature and updated billing
descriptions for greater clarity.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->