Elektra: Use Case: Edit configuration snippet

Elektra 0.8.24

Use Case: Edit configuration snippet

## Summary

- Title: Edit configuration snippet
- Scope: Entry Management
- Level: User Goal
- Actors: Authenticated user (snippet owner), Moderator
- Brief: Users can edit their own database entries. Moderators can edit all configuration snippets in the database, also the ones of other users.

## Scenarios

- Precondition: Authenticated, sufficient permissions
- Main success scenario: Changes to the configuration snippet have been stored to the database successfully. The user is informed about the success.
- Alternative scenario: The submitted inputs could not be validated or the entry for which changes are requested cannot be found. The user is informed about the error.
- Error scenario: Technical problems prevent the storage process from completing. The user is informed about the issue.
- Postcondition: Changes to the configuration snippet are stored in the database successfully and can be immediately seen in new requests of the snippet.
- Non-functional Constraints:
  - Moderative feature