Floating seat cap

The UX of having lots of SSO users join the platform, but experiencing a login error until we manually bump the seat limit, is not great.

On the other side, provisioning a buffer ahead of time just to avoid this possibility feels quite wasteful.

Consider having a floating usage-based seat limit for teams configured with SSO, and billing at the end of the month based on how many users were actually active, a la Slack or other similar usage-based tools.