Multiple layers of privacy-proxy.

[jhoyla]

A potential use case we might want to consider is multiple layers of privacy-proxy.
Consider a website that wants rate limits provided by Issuer₁ and Geo-location provided by Issuer₂.
Whilst the Origin could require the protocol to be run twice there isn't an obvious mechanism to ensure that the Client provides the same identity to Issuer₁ and Issuer₂.
Instead of doing this, before issuing any tokens Issuer₁ could forward the AccessTokenRequest to Mediator₂. This ensures that both mediators see the same request.
If tokens are issued by Issuer₂ and returned to Issuer₁ then Issuer₁ will issue tokens to the Client.

Something like this: