Elektra: Use Case: Undo/Redo

Elektra 0.8.24

Use Case: Undo/Redo

## Summary

- Title: Undo/Redo
- Scope: Configuration
- Level: User Goal
- Actors: User (usually a sysadmin)
- Brief: User undos/redos changes to a configuration.

## Scenarios

- Precondition: Modifying keys, Adding keys, Drag & Drop keys.
- Main success scenario: User successfully undos/redos a configuration change.
- Error scenario: Technical problems while configuring the instance. The user is informed about the problem.
- Postcondition: The updated configuration is persisted to the instance.
- Non-functional Constraints:
  - Every editor operation (preconditions) should be undoable