Ensure delete protection is enabled for Amazon Relational Database Service (Amazon RDS) Instances

Delete protection can provide assurance that a database cannot be deleted until the instance running that database is first altered to disable the setting. This is enabled by default when choosing the 'production' option during new database instance setup. For more information, see the AWS documentation.
References:
https://aws.amazon.com/about-aws/whats-new/2018/09/amazon-rds-now-provides-database-deletion-protection/

In AWS Console -

1. Sign in to the AWS Console and go to the AWS RDS Console.
2. In the RDS Dashboard, click on Databases.
3. Select Modify to modify the instance of your choice.
4. Modify deletion protection and click the 'Enable Deletion Protection' checkbox.

In Terraform -

1. In the aws_db_instance resource, set deletion_protection field to true.

References:
https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/db_instance#deletion_protection