| Elektra 0.11.0

Use Case: `Key` Metadata

# Summary

- Scope: `libelektra-core`
- Level: Developer Goal
- Actors: Core, Caller
- Brief: Access to `Key`'s metadata

# Scenarios

- Precondition:
  - `Key` has been created
- Main success scenario:
  - Caller requests metadata of `Key`
  - Core returns metadata of `Key` as modifiable `KeySet`
- Alternative scenario: -
- Error scenario: -
- Postcondition: -
- Non-functional Constraints: -