Create DNS for apps domain apex
Create DNS for apps domain apex

Create an alias DNS for the apps domain apex that points to the
router ELB. It must be an alias as we can't configure a CNAME for an
apex.
This was originally created in aws-account-wide-terraform:
https://github.gds/government-paas/aws-account-wide-terraform/blob/7656107b7b3a160acf4c82f44d0156cc0ad39bae/terraform-high/aws_hsts_api_gateway.tf#L92-L103
This should be removed by aws-account-wide-terraform before applying it
from paas-cf.

alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf