Fix id of Items, saving

CHDataManagement/Mock/Page+Mock.swift

@@ -28,13 +28,13 @@ extension Page {
                         lastModified: nil,
                         originalUrl: "projects/electronics/my-first-project/en.html"),
                     tags: [
-                        content.tags.first(where: { $0.id == "electronics" })!
+                        content.tags.first(where: { $0.identifier == "electronics" })!
                     ])
             ]
         }
 
         static var empty: Page {
-            Content.mock.pages.first(where: { $0.id == "my-id" })!
+            Content.mock.pages.first(where: { $0.identifier == "my-id" })!
         }
     }
 }