Create a Microsoft Teams online meeting attached to a Microsoft Graph calendar event

Steps

1. POST to /me/events (or /users/{id}/events) with isOnlineMeeting set to true and onlineMeetingProvider set to "teamsForBusiness".
2. Read the join link from the response's onlineMeeting.joinUrl property, not the deprecated onlineMeetingUrl field.
3. Ensure the calling app/token has Calendars.ReadWrite permission scoped appropriately (delegated vs application) — a missing scope can create the event without meeting details populated.
4. For finer meeting controls (lobby bypass, recording settings), create the onlineMeeting resource directly via POST /me/onlineMeetings and link it, rather than relying solely on event properties.
5. Once isOnlineMeeting is set true and the provider is chosen on an event, treat both as immutable — you cannot flip isOnlineMeeting back to false or change onlineMeetingProvider afterward.