| Elektra 0.11.0

Use Case: Create `KeySet`

# Summary

- Scope: `libelektra-core`
- Level: Developer Goal
- Actors: Core, Caller
- Brief: Caller creates new `KeySet` instance

# Scenarios

- Precondition: -
- Main success scenario:
  - Caller requests to create a new `KeySet`
  - Core instantiates an empty `KeySet` and returns it
- Alternative scenario: -
- Error scenario: -
- Postcondition:
  - `KeySet` exists and is usable by Caller
- Non-functional Constraints:
  - `KeySet` MUST be resizable after creation
  - `KeySet` SHOULD be efficient for small (~10) to larger (~100.000) sizes