The shareToken is a long DID key that looks something like this
Sharing keys is not good pattern, I think it's best to make do with some short delegation that will allow to wire up delegatio.
Also note that just like you can delegate access to your email, you could delegate to friends email. I think it might be a good idea to leverage that in fireproof. something along the lines of
js
if (cx.authorized) {
ctx.share(friendsEmail)
}
Now when account authorizes with friendsEmail
and pulls down delegations, this one will show up.