private void copyBody(CalendarEventModel eventModel, Map<String, Object> graphCalendar) {
    String notes = eventModel.getNotes();
    if (notes == null) {
      return;
    }
    Map<String, String> body = new HashMap<>();
    body.put("contentType", "HTML");
    body.put("content", notes);
    graphCalendar.put("body", body);
  }
Maps from a transfer event type to a Graph API event resource as defined by:
https://developer.microsoft.com/en-us/graph/docs/api-reference/v1.0/resources/event.
extensions/data-transfer/portability-data-transfer-microsoft/src/main/java/org/datatransferproject/transfer/microsoft/transformer/calendar/ToGraphEventTransformer.java