Ensure Multi-AZ is enabled for AWS Database Migration Service (DMS) instances

Multi-availability zone architecture can provide redundancy for a more resilient infrastructure. DMS instances can be configured in clusters that cross availability zones. For more information, see the AWS documentation.
References:
https://docs.aws.amazon.com/dms/latest/userguide/CHAP_ReplicationInstance.html

In AWS Console -

1. Sign in to the AWS Console and go to the AWS DMS Console.
2. Select Replication Instances in the navigation pane.
3. Select the instance you want to modify.
4. Modify Multi-AZ to enable it.

In Terraform -

1. In the aws_dms_replication_instance resource, set the multi_az field to true.

References:
https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/dms_replication_instance