AWS::Cognito::UserPoolDomain missing return value for the CloudFront target

I am missing the return value for the CloudFront target so that you could create a DNS record in the same template so that you could do this:

```yaml
DNS:
Type: AWS::Route53::RecordSet
Properties:
HostedZoneName: mydomain.com.
Name: myuserpool.mydomain.com.
Type: A
AliasTarget:
HostedZoneId: Z2FDTNDATAQYW2
DNSName: !GetAtt UserPoolDomain.DomainName

UserPoolDomain:
Type: AWS::Cognito::UserPoolDomain
Properties:
UserPoolId: !Ref UserPool
Domain: myuserpool.mydomain.com
CustomDomainConfig:
CertificateArn: !Ref CertificateArn
```

_Originally posted by @Nr18 in https://github.com/aws-cloudformation/aws-cloudformation-coverage-roadmap/issues/58#issuecomment-539652016_

Start with the AWS::Cognito::UserPoolDomain example in the issue and verify how its CloudFront target should be exposed for Route 53 AliasTarget.DNSName. Then locate the repository's coverage entry for this resource; done means the return value is available in the same template as shown and the behavior is covered by the relevant project checks.

Written by the indexing model from the issue text.