Ensure public access is disabled for AWS Redshift Clusters

Allowing unrestricted, public access to cloud services could open an application up to external attack. Disallowing this access is typically considered best practice.

In AWS Console -

1. Go to the Amazon Redshift console.
2. Select Clusters.
3. Select the cluster to which you are trying to connect.
4. Select Actions.
5. Select Modify publicly accessible setting to disable it.

In Terraform -

1. In the aws_redshift_cluster resource, set the attribute 'publicly_accessible' to 'false'.

References:
https://docs.aws.amazon.com/redshift/latest/mgmt/managing-clusters-vpc.html
https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/redshift_cluster#publicly_accessible