code: public static Mode applyFileUMask(Mode mode, String authUmask) {
      mode = applyUMask(mode, getUMask(authUmask));
      mode = applyUMask(mode, FILE_UMASK);
      return mode;
    }
docs: Applies the default umask for newly created files to this mode.
  
  @param mode the mode to update
  @param authUmask the umask to apply on the file
  @return the updated object