Provide external access with view/read-only

Provide external access with view/read-only permission without adding users to Connected project

The idea for this is to allow external users to simply view the iTwin model with no other permission to the Connected Project. For example, this could be used in a Bid/Tender phase to allow potential bidders to view the model without gaining access to the rest of the project. With this, we would want to be able to control whether or not the iTwin could be exported to IFC.