* Add additional information to `NotificationRepresenter` to be able to display:
* Begin of the insertionFinishEnd of the insertion Begin of the deletion  FinishEnd of the deletion date is in 2 days
* Begin of the insertionStartEnd of the insertion Begin of the deletion  StartEnd of the deletion date is today
* Work package is overdue since 2 days
* The information needs to be machine readable, not a fixed string
* Begin of the insertionThatEnd of the insertion Begin of the deletion  ThatEnd of the deletion way, the notification card can display the correct difference between the current time and the start/finish date which will change between looking at the card on one day and the next one. Begin of the insertion
* Does not need to be implemented but the format should be extensible to later also display activity information like
* Assignee set
* Assignee unset
* Assignee changedEnd of the insertion
* Begin of the insertionTheEnd of the insertion Begin of the deletion  TheEnd of the deletion information needs to reflect changes done to the work package after the notification is created.
* E.g. User is notified about the work package starting in 2 days. Another user moves the work package a week into the future. Then the notification card needs to say that it is starting in 9 days.
* Ensure the format works for other use cases, e.g.:
* Having a notification for the release notes of an OpenProject version update
* Having a notification for a downtime
* Having the assignee change (typically old value & new value & property) information as part of the notification
* Handle not having an actor for a notification (needs to be changed in API documentation as well)
* Adapt the API documentation