FeedAttributes define the types of data expected to be present in a Feed. A single FeedAttribute specifies the expected type of the FeedItemAttributes with the same FeedAttributeId. Optionally, a FeedAttribute can be marked as being part of a FeedItem's unique key.
Indicates that data corresponding to this attribute is part of a FeedItem's unique key. It defaults to false if it is unspecified. Note that a unique key is not required in a Feed's schema, in which case the FeedItems must be referenced by their feed_item_id.