feat(email-receiver): Lambda function receives SNS event (#262)

The Lambda function now receives a SNS event containing the SES event.

Use the following code to get the SES event:

```ts
export async function handler(event: AWSLambda.SNSEvent): Promise<void> {
  const ses = JSON.parse(event.Records[0].Sns.Message) as AWSLambda.SESMessage;
}
```

This removes a intermediary Lambda function that had an EventBridge destination, simplifying the architecture.

BREAKING CHANGE: The Lambda function of an `EmailReceiver` now receives a SNS event.

src/email-receiver/README.md

@@ -27,7 +27,7 @@ export class MyStack extends Stack {
 }
 ```
 
-Your Lambda function conveniently receives a [`AWSLambda.SESMessage`](https://www.npmjs.com/package/@types/aws-lambda)
+Your Lambda function receives a [`AWSLambda.SNSMessage`](https://www.npmjs.com/package/@types/aws-lambda)
 event:
 
 ```ts
@@ -36,11 +36,13 @@ import { SESMessage } from 'cloudstructs';
 
 const s3 = new S3({ apiVersion: '2006-03-01' });
 
-export async function handler(event: AWSLambda.SESMessage): Promise<void> {
+export async function handler(event: AWSLambda.SNSEvent): Promise<void> {
+  const ses = JSON.parse(event.Records[0].Sns.Message) as AWSLambda.SESMessage;
+
   // Download email
   const rawEmail = await s3.getObject({
-    Bucket: event.receipt.action.bucketName,
-    Key: event.receipt.action.objectKey,
+    Bucket: ses.receipt.action.bucketName,
+    Key: ses.receipt.action.objectKey,
   }).promise();
 
   // ... do something with email ...

src/email-receiver/receiver.ts

@@ -1,14 +1,12 @@
 import { Duration } from 'aws-cdk-lib';
 import * as lambda from 'aws-cdk-lib/aws-lambda';
-import * as destinations from 'aws-cdk-lib/aws-lambda-destinations';
 import * as logs from 'aws-cdk-lib/aws-logs';
 import * as s3 from 'aws-cdk-lib/aws-s3';
 import * as ses from 'aws-cdk-lib/aws-ses';
 import * as actions from 'aws-cdk-lib/aws-ses-actions';
 import * as sns from 'aws-cdk-lib/aws-sns';
 import * as subscriptions from 'aws-cdk-lib/aws-sns-subscriptions';
 import { Construct } from 'constructs';
-import { S3Function } from './s3-function';
 import { WhitelistFunction } from './whitelist-function';
 
 /**
@@ -97,13 +95,6 @@ export class EmailReceiver extends Construct {
       topic,
     }));
 
-    const s3Handler = new S3Function(this, 's3', {
-      logRetention: logs.RetentionDays.ONE_MONTH,
-      onSuccess: new destinations.LambdaDestination(props.function, {
-        responseOnly: true,
-      }),
-    });
-
-    topic.addSubscription(new subscriptions.LambdaSubscription(s3Handler)); // Notify
+    topic.addSubscription(new subscriptions.LambdaSubscription(props.function)); // Notify
   }
 }