aws_kinesis_firehose_delivery_stream resources should have server_side_encryption enabled by default

[scott-maclure-phx]

Why? Because compliance/config policy sets will pick up on encryption at rest violations.

See https://github.com/SumoLogic/terraform-sumologic-sumo-logic-integrations/blob/master/aws/kinesisfirehoseformetrics/kinesisfirehoseformetrics.tf#L97

And https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/kinesis_firehose_delivery_stream#server_side_encryption

Could be AWS managed key (default) or a CMK (pass the ARN into the module as an argument)?