emberjs/data — pull request #1679 by benedikt (2014-01-21 14:46:48+00:00)
Title: Add support for polymorphic embedded records to the EmbeddedRecordsMixin

The type of the embedded record is inferred using the `type` property of each embedded record. This behavior is customizable by overriding the `keyForEmbedded(relationship, data)` method on the serializer.