[Feature request] support CloudFront Alternate Domain Name

I have an issue where the alternate domain name set in cloudfront is not being set and is being removed when the stack is updated.
Steps to reproduce:
1. Deploy solution from this [link](https://console.aws.amazon.com/lambda/home?region=us-east-1#/create/app?applicationId=arn:aws:serverlessrepo:us-east-1:520945424137:applications/cloudfront-authorization-at-edge) and set an alternate domain name. No other option changed from default except alternate domain name. Not sure it matters but I am setting domain like portal.dev.example.com.
2. After deploy is complete the alternate domain name is not set on cloudfront distribution. The domain name is set manually along with the ssl cert and everything works OK at this point.
3. When the stack is updated, the alternate domain name and ssl cert previously set is removed from the cloudfront distribution. It did this when I changed the setting for HttpHeaders.

Use the linked AWS Serverless Application deployment to reproduce the missing alternate domain name, then update the stack with the HttpHeaders setting. Inspect how the CloudFront distribution handles the alternate domain name and SSL certificate during deployment and updates. Done means both settings are retained after the initial deployment and a later stack update.

Written by the indexing model from the issue text.