Use case:
The customer installs 3scale API Management on-premises using WILDCARD_DOMAIN=internal.example.com (this domain is used for all internal communication between 3scale components), so the default provider admin portal looks like 3scale-admin.internal.example.com. For external access to the admin portal though the customer uses a different domain: external.example.com.

The emails sent by system to admins sometimes include links to the admin portal, for example, View new signup in your 3scale Admin Portal that points to e.g. https://3scale-admin.internal.example.com/buyers/accounts/12345.

The request is to be able to configure the external admin portal domain (external.example.com), so that the links in the emails are pointing to it.