Fix null blob_path

Nested `expose` returns null unless it's a part
of Entity class

ee/app/serializers/dependency_entity.rb

 # frozen_string_literal: true
 
 class DependencyEntity < Grape::Entity
-  expose :name, :packager, :version
-  expose :location do
+  class LocationEntity < Grape::Entity
     expose :blob_path, :path
   end
+
+  expose :name, :packager, :version
+  expose :location, using: LocationEntity
 end

ee/spec/serializers/dependency_entity_spec.rb

@@ -18,10 +18,6 @@ describe DependencyEntity do
 
     subject { described_class.represent(dependency).as_json }
 
-    it { is_expected.to include(:name) }
-    it { is_expected.to include(:version) }
-    it { is_expected.to include(:packager) }
-    it { expect(subject[:location]).to include(:blob_path) }
-    it { expect(subject[:location]).to include(:path) }
+    it { is_expected.to eq(dependency) }
   end
 end