Generate multiple entities if a `KongCustomEntity` is attached to multiple other entities

[randmonkey]

Is there an existing issue for this?

• [X] I have searched the existing issues

Does this enhancement require public documentation?

• [X] I have added an Acceptance Criteria item for adding and/or adjusting public documentation (if applicable)

Problem Statement

A KongCustomEntity resource may be attached to multiple other entities via its parentRef plugin. We need to generate one entity for each referred other entity.

Proposed Solution

• Clone entity into multiple entities in the process of filling foreign fields
• Sort the entities from the same k8s KCE resource by the ID of foreign entity

Additional information

No response

Acceptance Criteria

• [ ] For each referred external entity of a KCE resource, a separate entity is generated
• [ ] The entities generated from the same KCE are sorted with a stable order