Use this data source to get the ARN of a certificate in AWS Certificate
Manager (ACM). The process of requesting and verifying a certificate in ACM
requires some manual steps, which means that Terraform cannot automate the
creation of ACM certificates. But using this data source, you can reference
them by domain without having to hard code the ARNs as input.
The acceptance test included requires an ACM certificate be pre-created
in and information about it passed in via environment variables. It's a
bit sad but there's really no other way to do it.