Check uniqueness of required fields in controller caches by Indexer instead of Store

[randmonkey]

Is there an existing issue for this?

• I have searched the existing issues

Problem Statement

For some of the resources, there is a uniqueness restraint on certain fields, like username of KongConsumer or prefix of KongVault.
To avoid conflicting resources be stored into cache, we can use Indexer instead of Store to store the objects and define the indexer to extract the unique fields, and reject the update to cache if the field is duplicate.

Proposed Solution

• Use Indexer to store KongConsumer, KongVault and other objects requires some fields to be unique
• Define IndexFunc to extract fields with uniqueness restraint as indices and reject object with dupe fields
• Update the status of the object if it is rejected by the reason of dupe field

Additional information

No response

Acceptance Criteria

• Use Indexer to store KongConsumer, KongVault and other objects having requirement of uniqueness on certain fields
• These objects with dupe field will be rejected to store into the controller cache
• If an object is rejected by dupe field, status can reflect this