AWS::RDS::DBCluster - Support importing RDS instances and clusters to CDK stack without downtime.

### Name of the resource

AWS::RDS::DBCluster

### Resource name

_No response_

### Description

It is not possible to import RDS instances and clusters into a CDK stack.

It is possible to do it via a snapshot, but this is not ideal and prohibits me from importing pre-existing databases (created with Terraform) to CDK. This approach requires downtime.

Is it in the "roadmap" to support importing these resources in the future?

Thanks!

### Other Details

_No response_

Start by reviewing the AWS::RDS::DBCluster resource and the CloudFormation import behavior described in the issue, including the snapshot-based approach and existing Terraform resources. Determine the scope needed to support importing RDS instances and clusters into a CDK stack without downtime; done means the supported workflow and requirements are clear and the import succeeds without a snapshot-induced outage.

Written by the indexing model from the issue text.