use database constraints

... in bookshop, orders, reviews
+ update package.json and package-lock.json as db constraints
  requires latest cds

reviews/package.json

@@ -18,6 +18,9 @@
         "[production]": { "kind": "enterprise-messaging" }
       },
       "db": { "kind": "sql" }
+    },
+    "features": {
+      "assert_integrity": "db"
     }
   }
 }