code: @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;
      });
    }
docs: Confirm a single uploaded file with the passed field name.
  
  @param sFieldName
  The field name to be confirmed. May be <code>null</code>.
  @return The (non-temporary) user data object for the resolved field name.
  May be <code>null</code> if the passed field name is not contained.
  @see #cancelUploadedFiles(String...)