Right now the only one allowed to edit a booking is the one who created it. This is especially a problem for example DrawIT, who makes bookings for the DrawIT group who succeeds them. This means that the new DrawIT group can't edit the booking since a member of last DrawIT made it. And the member of last DrawIT can't edit it since they are no longer member of DrawIT and thus has lost the ability to create, edit or delete bookings.
Right now the only one allowed to edit a booking is the one who created it. This is especially a problem for example DrawIT, who makes bookings for the DrawIT group who succeeds them. This means that the new DrawIT group can't edit the booking since a member of last DrawIT made it. And the member of last DrawIT can't edit it since they are no longer member of DrawIT and thus has lost the ability to create, edit or delete bookings.
The solution to this issue should be here: https://github.com/cthit/bookIT/blob/master/app/models/ability.rb#L17