Hidden circle option

[akrobatim]

There are two options for circles today. Public, as in any one can ask to jon, and Private, as in visible but you can only join via invite, and possibly some other restrictions. I think we need a third option, which is hidden, that is a circle that is only visible to its participants. This will allow teams to work in private on projects and more that they are not prepared to share just yet (or perhaps ever).