refactor: improve lookup challenge scaffolding and notebook guidance

Author: ricardohsmello

java/103_aggregation_pipeline_lookup.ipynb

@@ -128,7 +128,10 @@
    "metadata": {},
    "source": [
     "### 1. Fetch books with their associated reviews\n",
-    "[Solution here](https://mongodb-developer.github.io/sql-to-query-api-lab/docs/aggregation/lookup#-1-fetch-books-with-their-associated-reviews)"
+    "\n",
+    "Bonus: try adding a `$limit` stage as an extra improvement to reduce the output size.\n",
+    "\n",
+    "[Solution here](https://mongodb-developer.github.io/sql-to-query-api-lab/docs/aggregation/lookup#-1-fetch-books-with-their-associated-reviews)\n"
    ]
   },
   {
@@ -142,7 +145,18 @@
    },
    "outputs": [],
    "source": [
-    "// type your code here"
+    "// TYPE YOUR CODE HERE\n",
+    "\n",
+    "AggregateIterable<Document> result = books.aggregate(\n",
+    "    List.of(\n",
+    "        <REPLACE_WITH_LOOKUP_STAGE>               \n",
+    "    )\n",
+    ");\n",
+    "\n",
+    "// Iterate through the results\n",
+    "for (Document doc : result) {\n",
+    "    System.out.println(\"book: \" + doc.toJson());\n",
+    "}"
    ]
   }
  ],