The CRDCompatibilityRequirement API defines the ability to prune the defined CRD based on both API version and fields.

When admitting custom resources, we expect the webhook to load in the CRD schema from compatibility requirement and validate the request object with the desired schema validation.

For any field that isn't present, this should be stripped from the request.

The intention of this card is to implement the latter part of that, the field pruning so that a field unknown to the schema is not persisted on the accepted request.

DOD: includes thorough unit/integration tests.