Currently, to facilitate the file upload :

• add $file attribute to entity Assert as file
• add $path attribute to entity which stores the actual filename
  as advised
• use lifecyclecallbacks to automate file upload handling.
  and since the callbacks do not work if only file is changed
• add an updated field that is manually changed to make everything work.

All these amounts to 3 new attributes to facilitate the updating of
one field, which overall does not make practical sense.

Is there no way to use just one field for file handling
and by itself trigger the callbacks when it is changed ?