Integration/e2e tests for usage of custom entities

[randmonkey]

Is there an existing issue for this?

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Does this enhancement require public documentation?

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

Problem Statement

Split from custom entities #4556.
We need to add integration and e2e test cases to verify that KIC can reconcile KongCustomEntity CRs and translate then correctly to Kong configurations.

Proposed Solution

• Add a test cases for using custom entities (like degraphql_route) in integration tests

Additional information

No response

Acceptance Criteria

• integration/e2e tests can verify that plugins using custom entities supported correctly.