instead of having them already in the templates.

It doesn't always create a new room.

So that when a room is closed, a previously obscured chat doesn't become
visible again. Allowing this would force us to know which chat is visible, so
that we can falsify it's `hidden` attribute.

otherwise also the prototype's defaults gets overwritten.

Also... `num_unread` is now updated for groupchat messages in which the user is
mentioned.

and I'm not aware of a valid usecase for doing so.

Otherwise it gets rendered multiple times (at least during testing).