Google Apps Script that handles Hangout/Meet links, with automatic updates and primary calendar detection. See https://medium.com/@JoeSalowitz/how-to-add-google-calendar-hangouts-links-to-mac-and-ios-calendar-events-af365cd93a3c for original post.

moveHangoutLinks.js

function moveHangoutLinks() {
  var calendarId = Calendar.Calendars.get('primary').id;
  var now = new Date();
  var events = Calendar.Events.list(calendarId, {
    timeMin: now.toISOString(),
    singleEvents: true,
    orderBy: 'startTime',
    maxResults: 10
  });
  if (events.items && events.items.length > 0) {
    for (var i = 0; i < events.items.length; i++) {
      var event = events.items[i];
      if (event.hangoutLink) {
        hangoutUrl = event.hangoutLink + (event.hangoutLink.indexOf('?') == -1 ? '?' : '&') + 'authuser=' + calendarId;
        event.description = (event.description || '').replace(/^Hangout(\/Meet)?:.+$[\s]+/mg, 'Hangout/Meet: ' + hangoutUrl + '\n\n');
        Calendar.Events.update(event, calendarId, event.id);
      }
    }
  } else {
    Logger.log('No events found.');
  }
}