docs: @Nullable
    public UserDataObject confirmUploadedFile (@Nullable final String sFieldName)
    {
      return m_aRWLock.writeLocked ( () -> {
        if (StringHelper.hasText (sFieldName))
        {
          // Remove an eventually existing old UDO
          final TemporaryUserDataObject aUDO = m_aMap.remove (sFieldName);
          if (aUDO != null)
          {
            LOGGER.info ("Confirmed uploaded file " + aUDO);
            // Convert from temporary to real UDO
            return new UserDataObject (aUDO.getPath ());
          }
        }
        return null;
      });
    }