Allow a user to indicate that they are unavailable for a certain period of time and automatically delegate to another user the items that will be assigned during their absence. All existing items will remain assigned to the user. It is possible to cancel the delegation at any time.
Here is a mock up of the functionlity with the related notes:
On the left side there would be the list of delegation, on the right side the modal to be opened when a new delegation is set up.