chore(docs): Update mongodb code example for mongo singleton (#10683)

Co-authored-by: Nico Domino <yo@ndo.dev>

docs/pages/getting-started/adapters/mongodb.mdx

@@ -79,33 +79,43 @@ The MongoDB adapter does not handle connections automatically, so you will have
 
 ```ts filename="lib/db.ts"
 // This approach is taken from https://github.com/vercel/next.js/tree/canary/examples/with-mongodb
-import { MongoClient } from "mongodb"
+import { MongoClient, ServerApiVersion } from "mongodb";
 
 if (!process.env.MONGODB_URI) {
-  throw new Error('Invalid/Missing environment variable: "MONGODB_URI"')
+  throw new Error('Invalid/Missing environment variable: "MONGODB_URI"');
 }
 
-const uri = process.env.MONGODB_URI
-const options = {}
+const uri = process.env.MONGODB_URI;
+const options = {
+  serverApi: {
+    version: ServerApiVersion.v1,
+    strict: true,
+    deprecationErrors: true,
+  },
+};
 
-let client
-let clientPromise: Promise<MongoClient>
+let client;
+let clientPromise: Promise<MongoClient>;
 
 if (process.env.NODE_ENV === "development") {
   // In development mode, use a global variable so that the value
   // is preserved across module reloads caused by HMR (Hot Module Replacement).
-  if (!global._mongoClientPromise) {
-    client = new MongoClient(uri, options)
-    global._mongoClientPromise = client.connect()
+  let globalWithMongo = global as typeof globalThis & {
+    _mongoClientPromise?: Promise<MongoClient>;
+  };
+
+  if (!globalWithMongo._mongoClientPromise) {
+    client = new MongoClient(uri, options);
+    globalWithMongo._mongoClientPromise = client.connect();
   }
-  clientPromise = global._mongoClientPromise
+  clientPromise = globalWithMongo._mongoClientPromise;
 } else {
   // In production mode, it's best to not use a global variable.
-  client = new MongoClient(uri, options)
-  clientPromise = client.connect()
+  client = new MongoClient(uri, options);
+  clientPromise = client.connect();
 }
 
 // Export a module-scoped MongoClient promise. By doing this in a
 // separate module, the client can be shared across functions.
-export default clientPromise
+export default clientPromise;
 ```