**As** an OpenProject user
**I want** to be able to undo the last Begin of the insertionseveral actionsEnd of the insertion Begin of the deletion actionEnd of the deletion I took on a work package
**so** that I can easily recover the previous data.

**Acceptance criteria**

* Add an "undo" action that is displayed for the user making a change when a change is made.
* The undo action should revert back to the state prior to the last Begin of the insertionchange (and be able to revert the last several changes).End of the insertion Begin of the deletion change.End of the deletion

TBD:

* Begin of the insertionHow manyEnd of the insertion Begin of the deletion Are multipleEnd of the deletion steps of "undo" actions Begin of the insertionareEnd of the insertion necessary?
* Should other users be able to undo actions of a user?