If you have the High-Availability plan, we can set up a custom domain name such as you suggest.

The best way to do this is to open a support ticket with the fully qualified domain name (id.example.com, for example). We'll then create the cert on our end in AWS, and then we just have you create two DNS records on your end, which assures AWS the certificate is being created by people with the correct authority.

If you'd rather create the cert, it is possible for us to import your cert, but then you’ll need to be sure that you send us new certificates each time you are issued a new one, so it is more error prone.