Roles and permissions are introduced to restrict access to certain resources and
actions for specific applications. This is a security enhancement for the api.
A reference attribute is added to the representation of the Event,
Order, and Product resources.
It is meant to be used as a means of communication with consumers.
Product now contains a viewing_order attribute, which
specifies its order when products should be displayed as a list. This is per event. The products
in the response are also ordered by the viewing_order attribute.
Product now contains additional_information attribute.