Support KongCustomEntity to refer to resource in other namespace in spec.parentRef

[randmonkey]

Is there an existing issue for this?

• I have searched the existing issues

Does this enhancement require public documentation?

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

Problem Statement

Currently KongCustomEntity does not support referring to KongPlugin in other namespaces. We should enable KongCustomEntity to refer to resource (including but not limited to KongPlugin) in other namespaces.

Proposed Solution

• Allow KongCustomEntity to refer to KongPlugins in other namespaces if ReferenceGrant allows
• Reject in webhook or generate a translation failure if KongCustomEntity refers to resources in other namespaces without permission of ReferenceGrant

Additional information

No response

Acceptance Criteria

• KongCustomEntity referring to KongPlugin in another namespace with permission of ReferenceGrant can be accepted and translated
• ``KongCustomEntityreferring toKongPlugin` in another namespace without permission of `ReferenceGrant` is rejected by webhook or generate a translation failure