Restrict Sharing Proofs with Anyone Not Already Recognized User in Workfront

[#1]

Description -

In the financial services industry access management has become a critical issue. It would be great to have an easy way to restrict our users from sharing Proofs with  non-recognized users. We think we can restrict this somewhat, but once anyone is in the Proof, they can go to the share icon and type in anyone's email address and send a link to the Proof.

Current Behaviour - Today anyone tagged in a Proof can share it with anyone, anywhere. That presents a problem when you're trying to control access.