Pure extraction of an online-meeting join URL from a Graph event. Prefers the structured
onlineMeeting.joinUrl, then the legacy flat onlineMeetingUrl, then the first Teams meetup-join
URL found in the event body (HTML or text). Returns undefined when no join URL is present.
Pure extraction of an online-meeting join URL from a Graph event. Prefers the structured
onlineMeeting.joinUrl, then the legacy flatonlineMeetingUrl, then the first Teamsmeetup-joinURL found in the event body (HTML or text). Returnsundefinedwhen no join URL is present.