It is not a built-in functionality however it can be achieved with custom code and a valid FB token. The token can be produced with the extended embeds addon and I can probably wrap up some code for it in a few days if you are still interested, great idea for a new...
If I understand correctly what you are asking. On the app domain, you should add your website(s) domain(s) and on namespace invent a unique identifier for your app it can also be your domain name without “.com”