Added mongodb aggregateRaw caveats

content/200-orm/200-prisma-client/150-using-raw-sql/200-raw-queries.mdx

@@ -851,3 +851,18 @@ const result = await prisma.user.aggregateRaw({
 
 - `pipeline`: An array of aggregation stages to process and transform the document stream via the [aggregation pipeline](https://www.mongodb.com/docs/manual/reference/operator/aggregation-pipeline).
 - `options`: Additional options to pass to the [`aggregate` command](https://www.mongodb.com/docs/manual/reference/command/aggregate/#command-fields).
+
+:::info
+#### Caveats
+
+When working with custom objects like `ObjectId` or `Date,` you will have to pass them according to the [MongoDB extended JSON Spec](https://www.mongodb.com/docs/manual/reference/mongodb-extended-json/#type-representations).
+Example: 
+```ts no-lines
+const result = await prisma.user.aggregateRaw({
+  pipeline: [
+    { $match: { _id: { $oid: id } } }
+//                     ^ notice the $oid convention here 
+  ],
+});
+
+```