Remove PKI

[ianopolous]

The PKI provides unique global usernames, but is a single point of failure. the original motivation 10 years ago was to provide similar UX to existing social networks for adding a friend - add me on peergos I'm "ianopolous". But many modern social apps have moved on from this UX and instead have people share a friend URL or scan a QR code. We can remove the PKI if these links/qr codes have the public identity key of the user being friended.

Users then need to publish a mapping from their identity key to their current server's peer-id. This could be done using IPNS or pkarr or similar as long as resolution times are < 1s. The values can be cached indefinitely and only need to be looked up again if the server stops responding (e.g. if they change host).

This would also allow us to remove the current possibility for follow request spam, by letting users make these follow request URLs single use.