Ensure at-rest server side encryption (SSE) is enabled for data stored in AWS Kinesis Server

AWS Kinesis Server without server side encryption (SSE) can impact the confidentiality of data at-rest.

In Terraform -

1. In the aws_kinesis_firehose_delivery_stream resource, set the server_side_encryption.enabled field to true.
2. If using a customer-managed key, set the key_type as CUSTOMER_MANAGED_CMK and the key_arn to the appropriate value.

References:
https://docs.aws.amazon.com/firehose/latest/dev/encryption.html
https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/kinesis_firehose_delivery_stream#server_side_encryption