Redesign how recursive deletes are handled

Recursive deletion on a sub tree raise several issues :

• how security check are done : use should not being able to delete a sub tree if he does not have the rights on some of the sub folders
• associated versions should all be removed

To solve the issue, we need to redesign the whole system since :

• low level logic embedded in SQL
  • can create performance issues
  • does not allow to have pluggable logic
  • can not be reused for non SQL backend
• async processing is usually done in a system security context

The redesign should take care about :

• trash state
• soft delete