Sends the beta invitation email from support@gradesend.com (install link, setup steps, test checklist). One recipient at a time, capped at 20/day, every send logged.

Gates who can buy the Pro (DAEP) plan on the subscribe page. Only add a district once its DAEP adapter is built in the extension — listing it here makes it purchasable immediately. Deactivate instead of deleting so history stays intact.