Azure Container Registry domain name label scope

Whilst experimenting with our AKS support I needed to create an ACR registry and I noticed this option on the ACR creation page in the portal:

This allows us to control the name reuse scope. Need to investigate what level we are using. it probably makes the most sense to be the most strict here to avoid conflicts and squatting (best security posture).

But we need to think through the implications to swapping to this by default vs. opt in and whether we need some extra API surface on AddAzureContainerRegistry(...).