Enforce reseller disk limits when overselling is allowed and/or unlimited options are allowed.

As web-hosting provider, I would like to be able to enforce the total disk space a reseller can use when overselling or unlimited options are allowed, so that we can avoid confusion from customers who don't understand the notion of overselling and make reseller accounts more attractive.

I believe this might be possible by creating a user group (eg.: myreseller-users or quota-1234 ) and adding it to reseller's users then applying a quota to that group.