when inviting people to a project, and they're not registered yet, let them receive a link (either directly or email), and when link is used, their account is automatically created, verified, and password is sent to their email, they're automatically logged in, and shared project appears. (all in < 1 second).
if already registered, let them automatically log in if cookie present and receive project.
websockets: automatically receive shared items if logged in, pop up in console.
make it dead simple: