Add unlogged (guest) access

[gahabeen]

Summary

Give access to a document via a unique token.
The access can only have a get right (read).
We can imagine giving permissions to the relations inside the document with the same read right.

Mechanisms could be:

• create a session for this document
• generate a session token (hence specific to the dixit document)

This way the token can have an easy expiration management system.

Basic example

db.document('emails', '123').share()

Motivation

It's a fairly common feature that lets you share some information with external users.