fix: address all review feedback

- Moved CorsOptions type to types/rest.ts
- Moved DEFAULT_CORS_OPTIONS to constants.ts
- Fixed middleware to mutate existing headers
- Updated tests with Prepare/Act/Assess pattern
- Removed example files (will add in docs PR)
- Fixed all linting issues
- Converted functions to arrow functions

Author: dani-abib

examples/snippets/event-handler/rest/cors_basic_usage.ts

@@ -1,6 +1,9 @@
 import type { GenericLogger } from '@aws-lambda-powertools/commons/types';
 import { isRecord } from '@aws-lambda-powertools/commons/typeutils';
-import { getStringFromEnv, isDevMode } from '@aws-lambda-powertools/commons/utils/env';
+import {
+  getStringFromEnv,
+  isDevMode,
+} from '@aws-lambda-powertools/commons/utils/env';
 import type {
   OnPublishHandler,
   OnSubscribeHandler,
@@ -31,7 +34,7 @@ class Router {
    * Whether the router is running in development mode.
    */
   protected readonly isDev: boolean = false;
- 
+
   public constructor(options?: RouterOptions) {
     const alcLogLevel = getStringFromEnv({
       key: 'AWS_LAMBDA_LOG_LEVEL',

examples/snippets/event-handler/rest/cors_custom_config.ts

@@ -1,7 +1,7 @@
 export { AppSyncGraphQLResolver } from './AppSyncGraphQLResolver.js';
 export {
-  ResolverNotFoundException,
   InvalidBatchResponseException,
+  ResolverNotFoundException,
 } from './errors.js';
 export {
   awsDate,

examples/snippets/event-handler/rest/cors_dynamic_origin.ts

@@ -87,3 +87,20 @@ export const PARAM_PATTERN = /:([a-zA-Z_]\w*)(?=\/|$)/g;
 export const SAFE_CHARS = "-._~()'!*:@,;=+&$";
 
 export const UNSAFE_CHARS = '%<> \\[\\]{}|^';
+
+/**
+ * Default CORS configuration
+ */
+export const DEFAULT_CORS_OPTIONS = {
+  origin: '*',
+  allowMethods: ['DELETE', 'GET', 'HEAD', 'PATCH', 'POST', 'PUT'],
+  allowHeaders: [
+    'Authorization',
+    'Content-Type',
+    'X-Amz-Date',
+    'X-Api-Key',
+    'X-Amz-Security-Token',
+  ],
+  exposeHeaders: [],
+  credentials: false,
+} as const;