code: @Override
      public Calendar add(VJournal component) {
          Calendar add = wrap(Method.ADD, component);
          add.validate();
          return add;
      }
docs: <pre>
  3.5.2.  ADD
  
  The "ADD" method allows the "Organizer" to add one or more new
  instances to an existing "VJOURNAL" using a single iTIP message
  without having to send the entire "VJOURNAL" with all the existing
  instance data, as it would have to do if the "REQUEST" method were
  used.
  
  The "UID" must be that of the existing journal entry.  If the "UID"
  property value in the "ADD" is not found on the recipient's calendar,
  then the recipient MAY treat the "ADD" as a "PUBLISH".
  
  When handling an "ADD" message, the "Attendee" treats each component
  in the "ADD" message as if it were referenced via an "RDATE" in the
  main component.  There is no response to the "Organizer".
  </pre>