Proposal for use cases and threat models

[dtheodorakis]

Initial draft: https://github.com/antifraudcg/proposals/blob/main/use-cases/use-cases.md

[ianbjacobs]

Moved to: https://docs.google.com/document/d/1GXX3QkQQCT0h75K5LdML8ap4qZTMSD6tDPWz16dUDno/edit#heading=h.ar986mhy7x6q

(And now moved back to https://github.com/antifraudcg/proposals/blob/main/use-cases/use-cases.md )

[dvorak42]

Closing this as it has been adopted as https://github.com/antifraudcg/use-cases/.