Serverless RDS without a proxy example

Hi. lambda-function-connect-rds-iam seems to require an RDS Proxy. SDK v2 seems to have dropped support for non-proxy RDS. How does one use IAM authentication for RDS serverless without an RDS Proxy instance, which is very expensive? You can still do this via the CLI, and it was well-documented for SDK v1. E.g. see https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/UsingWithRDS.IAMDBAuth.Connecting.Java.html.

Start by reviewing the lambda-function-connect-rds-iam snippet and the linked AWS IAM database authentication documentation. Done means providing a serverless RDS example that uses IAM authentication without requiring an RDS Proxy, while matching the repository's existing snippet format.

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