code: private String generateCopyUidResponseCode(ImapSessionFolder currentMailbox,
                                                 List<Long> copiedUidsFrom, List<Long> copiedUidsTo) {
          StringBuilder copyuidResponseCode = new StringBuilder("COPYUID").append(SP).
                  append(currentMailbox.getUidValidity()).append(SP).
                  append(IdRange.uidsToRangeString(copiedUidsFrom)).append(SP).
                  append(IdRange.uidsToRangeString(copiedUidsTo));
  
          return copyuidResponseCode.toString();
      }
docs: Generates <b>COPYUID</b> response code
  (see <a href="http://tools.ietf.org/html/rfc2359#page-4">http://tools.ietf.org/html/rfc2359</a>)
  using format : <i>COPYUID UIDVALIDITY SOURCE-UIDS TARGET-UIDS</i>.
  
  For example <i>COPYUID 38505 304,319,320 3956,3957,3958</i>
  
  @param currentMailbox imap folder which is target of copy command
  @param copiedUidsFrom List of source uids which was successfully copied
  @param copiedUidsTo   List of message uids which was successfully copied
  @return response code