New privacy mode: Unlisted

[ssobczak]

I want to send a link to my note to a friend, who doesnt have an account. I don't want to make the note public.

This could be implemented in two ways:

1. simple: just 4th permission mode on each Memo - visible if you have a link, but not searchable and not visible in any list
2. fine-grained: each share creates unique link with token, which can be revoked and have exipration date

I could implement this, would this be an useful feature? I didnt find any guidelines on which approach may be prefferable, but I guess simplicity is one of the core assumptions in the project, so I guess the simple version would be prefferred.