Add custom cancan abilities on top of Spree

ability_decorator.rb

class AbilityDecorator
  include CanCan::Ability

  def initialize(user)
    #############################
    can :destroy, LineItem do |item|
      item.order.user == user
    end
    #############################
    can :read, Artwork do |artwork|
      artwork.order && artwork.order.user == user
    end
    can :update, Artwork do |artwork|
      artwork.order && artwork.order.user == user
    end
    #############################
    can :read, ArtworkRevision do |revision|
      revision.order && revision.order.user == user
    end
    can :update, ArtworkRevision do |revision|
      revision.order && revision.order.user == user
    end
    #############################
  end
end

Ability.register_ability(AbilityDecorator)