Manual delegation

As a user I can delegate someone else on a task I am assigned. I click on the delegate button. In a popup, I can choose a user, that is added on the task to the list of "delegated". As a consequence, this user is assigned the task too and benefit from the temporary permissions he should be assigned for correctly performing the task. He also receives a notification. If he is the one who processes the tasks (i.e. who closes it) there will be a specific translated entry in the audit log : "The task ABC was processed by XXX mandated by YYY, comment : ...