ACK RDS controller v1.60 compare DatabaseInsightsMode with null value

[Julian-Chu]

Describe the bug

rds controller v1.60 introduce the new DatabaseInsightsMode support, but it causes existing DBInstance resources becomes not synced, because it doesn't ignore when spec.DatabaseInsightsMode is null (it's new field, so existing DBinstance doesn't have any default value).

{
    ..........
    "diff": [
        {
            "Path": {
                "Parts": [
                    "Spec",
                    "DatabaseInsightsMode"
                ]
            },
            "A": null,
            "B": "standard"
        }
    ]
}

Steps to reproduce

deploy a DBInstance without DatabaseInsightsMode field

Expected outcome
A concise description of what you expected to happen.

Environment

• Kubernetes version
  1.32
• Using EKS (yes/no), if so version?
  yes, eks.16
• AWS service targeted (S3, RDS, etc.)
  RDS

[github-actions]

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[james-callahan]

I also posted this at aws-controllers-k8s/rds-controller#235 (comment)

could you share a DBInstance manifest that recreates this behavior in this #2622?

The DBInstance for the one in my logs in the above link is:

apiVersion: rds.services.k8s.aws/v1alpha1
kind: DBInstance
metadata:
  name: tkdb-merkle-db-instance1
spec:
  caCertificateIdentifier: rds-ca-ecc384-g1
  dbClusterIdentifier: tkdb-merkle-db
  dbInstanceIdentifier: tkdb-merkle-db-1
  dbInstanceClass: db.r6g.xlarge
  engine: aurora-postgresql

existing DBInstances after upgrading the controller

I saw it on existing DBInstances after upgrading the controller