[keyserver] display copyable url for qr code auth

Summary:
if a user is on a simulator or emulator they can't just scan the QR code, so we display the URL that's embedded in the QR Code so it can be copied

Depends on D12618

Test Plan: Confirmed that the URL displayed in my terminal above the QR Code

Reviewers: ashoat

Reviewed By: ashoat

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D12619