[CalendarServer-users] Assign Delegate/Proxy for User principal

I am certain this subject has been beaten to death - but without a searchable archive I can't seem to zero in on the exact solution. I am running latest DCS with XML File Directory Service. I want to define user "B" and give them read/write access to the calendars in user A's store. I have tried defining a proxy on the user principal object but it appears that users cannot have proxies. Do I really need to define user A as a resource principal? Sorry if I am being thick here. I have researched hours on this subject and still do not have a definitive answer on defining delegates for a user using XML File Repository. Thanks in advance. Corey