No property info provided for entity id - affects Search API

I am far from an expert of all the magic that goes on in an entity definition, but I think there is a problem with the fact that shopify.entity.inc does not provide property information for the 'id' field. This causes problems with search_api (see related #2666436: Search API support).

Steps to reproduce:
1. Create a new Search API index.
2. Add any field, 'title' for example.

The watchdog entry is like:

SearchApiException while updating the fields of index Test Products on server FDL Database Search Server: Entity type Shopify Product doesn't specify a type for the id property. in SearchApiDbService->fieldsUpdated() (line 732 of .../search_api_db/service.inc).

I traced the problem to the getIdFieldInfo method of SearchApiEntityDataSourceController. This calls to entity_get_property_info and no info is being returned for the 'id' property.

This might be a problem for other modules that are expecting property info for 'id'.