After many unwanted deletion of expenses sheet, bin for expenses sheets has finally been implemented. It is now impossible for users to delete directly an expenses sheet: the sheet is marked as deleted and automatically destroyed 30 days after its last edition, unless the user recovers it before. The action of deleting is now more coherent with other actions as it is undoable.
B: when user opens sheet without admin permissions, only user's expenses should be showed at first Upgrade to Python 2.7 using Google Appengine High Replication Datastore