RestKit/RestKit — pull request #596 by mcfedr (2012-03-13 07:44:57+00:00)
Title: support for mapping -> to many relationships by primary key

This makes the connectRelationship:withObjectForPrimaryKeyAttribute: work when the attribute is an array of ids.
It also changes how the relationship is done so that objects that have only just been created can be connected to.
For a structure such as
{
items: [{id: 1}, {id: 2}, {id: 3}],
itemgroups: [{items: [1, 2]}, {items:[2, 3]}]
}