Master admin can see the provider accounts admin portal (Admin domain) domains (see screenshot), however they can't change these domains.

There should be a way to change these domains using UI and API.

Things that need to generate error message:

• domain is already being used
• [developers add more info to this list please]

Let's document this here (see also this doc):
Who is this for - who will use it? Who should be able to use it? For RHOAM too?
What problem does it solve? For on-prem folks?
Limitation? (For example, only for SaaS, only for certain customers, etc.)
Do we provide it as a service? a support tool?
What could this break? for SaaS? for on-prem? for RHOAM?