### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

When you publish a message to SNS without a *body* (e.g. only attributes) it succeeds.

### Expected Behavior

Trying to publish a message without a *body* should fail (at least it does when trying to do this in AWS)

### How are you starting LocalStack?

Custom (please describe below)

### Steps To Reproduce

#### How are you starting localstack (e.g., `bin/localstack` command, arguments, or `docker-compose.yml`)

using Java testcontainers...

#### Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)

```bash
#!/bin/sh
 
queue_arn=$(awslocal sqs create-queue --queue-name $QUEUE_NAME --output text)
echo "Queue ARN: $queue_arn"

topic_arn=$(awslocal sns create-topic --name $TOPIC_NAME --output text)
echo "Topic ARN: $topic_arn"

subscription_arn=$(awslocal sns subscribe \
    --attributes RawMessageDelivery=true \
    --topic-arn "$topic_arn" \
    --protocol sqs \
    --notification-endpoint "$queue_arn" \
    --output text)
echo "Subscription ARN: $subscription_arn" 
```


### Environment

```markdown
- OS: OSX 11.5.2
- LocalStack: 0.13.0
- Docker Desktop: v20.10.8
```


### Anything else?

_No response_
def forward_request(self, method, path, data, headers):
                records.append((json.loads(to_str(data)), headers))
                return 200
        records = []
        local_port = get_free_tcp_port()
        proxy = start_proxy(local_port, backend_url=None, update_listener=MyUpdateListener())
        wait_for_port_open(local_port)
        queue_arn = "%s://localhost:%s" % (get_service_protocol(), local_port)
        self.sns_client.subscribe(TopicArn=self.topic_arn, Protocol="http", Endpoint=queue_arn)
        def received():
            self.assertEqual(records[0][0]["Type"], "SubscriptionConfirmation")
            self.assertEqual(records[0][1]["x-amz-sns-message-type"], "SubscriptionConfirmation")
            token = records[0][0]["Token"]
            subscribe_url = records[0][0]["SubscribeURL"]
            self.assertEqual(
                subscribe_url,
                "%s/?Action=ConfirmSubscription&TopicArn=%s&Token=%s"
                % (external_service_url("sns"), self.topic_arn, token),
            )
            self.assertIn("Signature", records[0][0])
            self.assertIn("SigningCertURL", records[0][0])
        retry(received, retries=5, sleep=1)
        proxy.stop()
    def test_attribute_raw_subscribe(self):