docs(idempotency): add callout about undefined early return (#3055)

Co-authored-by: Leandro Damascena <leandro.damascena@gmail.com>

Author: dreamorosi

docs/utilities/idempotency.md

@@ -206,6 +206,8 @@ Similar to the `makeIdempotent` function wrapper, you can quickly make your Lamb
     --8<-- "examples/snippets/idempotency/types.ts:3:16"
     ```
 
+For the middleware to work, your Lambda function handler must return a value different from `undefined`. This is a [known limitation of the early return feature in Middy.js](https://github.com/middyjs/middy/issues/1236). If your use case requires early returns, you can use the `makeIdempotent` function wrapper instead.
+
 ### Choosing a payload subset for idempotency
 
 Use [`IdempotencyConfig`](#customizing-the-default-behavior) to instruct the idempotent decorator to only use a portion of your payload to verify whether a request is idempotent, and therefore it should not be retried. When dealing with a more elaborate payload, where parts of the payload always change, you should use the **`eventKeyJmesPath`** parameter.

packages/idempotency/src/middleware/makeHandlerIdempotent.ts

@@ -1,18 +1,18 @@
-import { IdempotencyHandler } from '../IdempotencyHandler.js';
-import { IdempotencyConfig } from '../IdempotencyConfig.js';
 import {
-  cleanupMiddlewares,
   IDEMPOTENCY_KEY,
+  cleanupMiddlewares,
 } from '@aws-lambda-powertools/commons';
 import type {
-  AnyFunction,
-  IdempotencyLambdaHandlerOptions,
-} from '../types/IdempotencyOptions.js';
-import type {
+  JSONValue,
   MiddlewareLikeObj,
   MiddyLikeRequest,
-  JSONValue,
 } from '@aws-lambda-powertools/commons/types';
+import { IdempotencyConfig } from '../IdempotencyConfig.js';
+import { IdempotencyHandler } from '../IdempotencyHandler.js';
+import type {
+  AnyFunction,
+  IdempotencyLambdaHandlerOptions,
+} from '../types/IdempotencyOptions.js';
 
 /**
  * @internal
@@ -90,6 +90,11 @@ const shouldSkipIdempotency = (request: MiddyLikeRequest): boolean => {
  * ).use(makeHandlerIdempotent({ persistenceStore: dynamoDBPersistenceLayer }));
  * ```
  *
+ * For the middleware to work, your Lambda function handler must return a value different from `undefined`.
+ * This is a [known limitation of the early return feature in Middy.js](https://github.com/middyjs/middy/issues/1236).
+ *
+ * If your use case requires early returns, you can use the {@link index.makeIdempotent | makeIdempotent()} function wrapper instead.
+ *
  * @param options - Options for the idempotency middleware
  */
 const makeHandlerIdempotent = (