Key rotation workflow

### Problem description
Security best practices recommend adhering to a periodic key rotation schedule. Frequently internal security and compliance policies mandate and enforce this practice. Guardian does not provide facilities for this action, which may affect its adoption.

### Requirements
Implement UI and back-end functionality to rotate the keys used throughout Guardian such that:

- the execution of the key rotation is triggered manually by a user
- the system automatically identifies the keys that are under control of the user
- user can select the subset (or all) keys which hi/she controls to be rotated

### Definition of done

- The functionality is implemented as described above
- Appropriate documentation is created

### Acceptance criteria
Users can manually rotate 'their' keys