Implement finalizer addition for CPMS

Background

To ensure that the CPMS has an opportunity to clean up owner references on machines owned by the CPMS, it should add a finalizer to the CPMS.

The code needs to be implemented here  and it should pass the following tests  as well as any tests in here  which relate to finalizers.

Steps

• Review the tests cases and function description to understand what the expected behaviour is
• Implement the behaviour of the function based on prescribed behaviour in the tests
• Ensure linting passes (make lint) and think about the code layout, it is clean?
• Consider any additional tests that may need to be added

Stakeholders

• Cluster Infra (Joel)

Definition of Done

• Code has been reviewed and merged, Finalizer is added to CPMS before any work is carried out

• Docs

• N/A

• Testing

• Existing unit tests should be sufficient, but others may be added