Generic Roles in Shopping Cart

[Chris Howe]

I'm needing to restrict a custom roleTypeId to 1 per shopping cart and I'm not 
finding a way to do that. Would there be any objection to changing the way the 
roles are handled in the shopping cart?  I would like to change all of the 
roles that should be restricted to 1 per shopping cart from specified variables 
to a HashMap(String roletypeId, String partyId) in contrast to the 
additionalPartyRole of HashMap(String roleTypeId, List(String partyId)).