Support granting view access to your private site to a list of other Tiddlyhost users

[simonbaird]

Probably should require that those users have set their username, (rather than allow specifying by email address), so that personal email addresses as less directly exposed.

Stretch goal (maybe to be tracked in another issue): Allow inviting people by email to view a private site. The email should explain that they'll need to sign up if they haven't already.

(This might be a feature in the future for users on a non-free Tiddlyhost plan.)

[simonbaird]

Considerations:

• Should we introduce groups or organizations?
• Do groups then need group admins?
• What about allowing write access as well? It's problematic since Tiddlyhost (and TiddlyWiki) are generally not good for multiuser, but still...

[simonbaird]

Another idea: Grant view access to an otherwise private site via a generated (non-guessable) url that you can share with only those who you want to see it, and that you can revoke when you want to.