fix: Safecheck Object.entries for APIGatewayProxyEventHeaders (#93)

* fix: check if the event.multiValueHeaders exists before attempting to iterate it

* fix: checks if event.headers exists before attempting to iterate it.

* server: handle API Gateway REST API event without multiValueHeaders

---------

Co-authored-by: Frank <[email protected]>

Author: breningham

.changeset/nervous-bananas-remember.md

@@ -0,0 +1,5 @@
+---
+"open-next": patch
+---
+
+server: handle API Gateway REST API event without multiValueHeaders

packages/open-next/src/adapters/event-mapper.ts

@@ -260,12 +260,12 @@ function normalizeAPIGatewayProxyEventHeaders(
   event.multiValueHeaders;
   const headers: Record<string, string> = {};
 
-  for (const [key, values] of Object.entries(event.multiValueHeaders)) {
+  for (const [key, values] of Object.entries(event.multiValueHeaders || {})) {
     if (values) {
       headers[key.toLowerCase()] = values.join(",");
     }
   }
-  for (const [key, value] of Object.entries(event.headers)) {
+  for (const [key, value] of Object.entries(event.headers || {})) {
     if (value) {
       headers[key.toLowerCase()] = value;
     }