Current state:
- In batch provisioning, sendWelcomeEmail is a boolean only (send now or not at all). It cannot target a future date/time.
- The transition object on PUT /extension/{id} (sendWelcomeEmailsToUsers / sendWelcomeEmail) is also boolean only, with no scheduled datetime.
- The "Schedule invite" option (pick a date/time) exists only in the Admin Portal Add User wizard, not in any API.

Use case:
We provision new hires via the batch-provisioning API ahead of their start date. We want the activation invite to land on the start date, not at provision time. Today, the only way to schedule that is manually in the Admin Portal, or by building an external scheduler that fires a transition call on the start date. Native API support for a scheduled invite would let us fully automate onboarding without an external cron job or a manual portal step.

Requested capability:
A scheduled-invite parameter on user provisioning or the extension transition, for example:
"transition": { "sendWelcomeEmailsToUsers": true, "scheduledTime": "2026-07-06T13:00:00Z" }
or an equivalent scheduled-activation field, matching the Admin Portal's existing "Schedule invite" behavior.