Skills only to be rated or marked attained by employee

Summary:

Skills shall only be rated and marked attained by the employee themselves, not by others, especially not by the line manager.

Content:

Our client needs to give complete control over what skills an and what level employee has to the employees themselves.

The only possible exception would be if a Core Skill or Role Skill was assigned by the manager (but that is for now not very relevant yet).

So, how can we set up Skills Center, so that when someone else rates a skill (like the manager, or a co-worker), that the skill's validation level doesn't change, and their rating does not affect visible rating? On the other hand, the employee should be able to assess their own skill level and determine whether it is attained or not any time.