Allow path in an edm:key to also use a primitive property of a non null-able navigation property (recursively) of the entity type.

Allow the path expression to include references to unique, immutable, primitive (i.e., key) properties of non null-able, immutable navigation properties (recursively). 8.3.1 Attribute Name could be simply amended as in: The edm:PropertyRef element MUST specify a value for the Name attribute which MUST be a path expression resolving to a primitive property of the entity type itself or to a primitive property of a complex or a single-valued, non-nullable navigation property (recursively) of the entity type. The names of the properties in the path are joined together by forward slashes. Semantics: In JSON payloads: 1) The id must be written, even in minimal metadata, or 2) The nav properties must be expanded to include at least the related ids (service could default expand to include the related id fields.) You can only create the entity if: a. You include a link to an existing related entity containing the key value, or b. You do a deep insert that includes the related entity You can't change the relationship to the related entity containing the key value (so it would have to be single, non-nullable, and immutable) The referenced property(ies) on the related entity must be immutable and must be unique (i.e., are generally a key of the related entity) Deleting the related entity deletes the entity whose key referenced a property of that entity