With expression enabled, having /Customer<a>/Order<b>/id, /Customer<a>/Order<b>/Item<c> => NotifEmail<a>/body

For each Customer, I want to create an order detail mail body.
 Dear Customer<0>
 Detail of your Order<0>.id is following:
 Item<0>.name: Item<0>.quantity 
 Item<1>.name: Item<1>.quantity
 Item<2>.name: Item<2>.quantity
 Detail of your Order<1>.id is following:
 Item<0>.name: Item<0>.quantity
 Item<1>.name: Item<1>.quantity
 Item<2>.name: Item<2>.quantity

How do we express this in AtlasMap???

"Map values from a collection and apply a transformation on a collection(s) e.g.

Person<a>/name<b>/givenName -> User<a>/name (concat name<b>/givenName)

=> User<a>/name will contain ""givenName1 givenName2..."" for each person."