Hi

I have issues creating sns subscriptions through Cloudformation. If I attempt to include a `AWS::SNS::Subscription` resource in a Cloudformation template and run `create-stack` then I get a 500 Internal Server error. The full template:

```
AWSTemplateFormatVersion: '2010-09-09'
Description: 'Test'
Resources:
  MySnsTopic:
    Type: AWS::SNS::Topic
    Properties:
      TopicName: MySnsTopic
  MySnsTopicSubscription:
    Type: AWS::SNS::Subscription
    Properties:
      Protocol: sqs
      TopicArn: !Ref MySnsTopic
      Endpoint: !GetAtt
        - MySqsQueue
        - QueueArn
  MySqsQueue:
    Type: AWS::SQS::Queue
    Properties:
      QueueName: MySqsQueue
```

If I replace the references with hard-coded arns like this:

```
TopicArn: arn:aws:sns:eu-west-2:123456789012:MySnsTopic
Endpoint: arn:aws:sqs:elasticmq:000000000000:MySqsQueue
```

Then I get no errors but I get a warning:

`No moto Cloudformation support for AWS::SNS::Subscription`.

I can get around this issue by creating the subscription when creating the topic but the issue there is that I cannot add any attributes and in my case I need `RawMessageDelivery` set to true. So my questions are:

1. Is there no support to create `AWS::SNS::Subscription` resources through Cloudformation or am I doing something wrong?
2. If support is not there can I request it as a new feature?
3. Any suggestions on how I can work around this? I know I could do this through a script at startup but would like to not have any additional script steps other than deploying the Cloudformation stack.

<!-- Love localstack? Please consider supporting our collective:
👉  https://opencollective.com/localstack/donate -->
"""Downloads file at url to the given path"""
    
    
    s = requests.Session()
    r = s.get(url, stream=True, verify=verify_ssl)
    total = 0
    try:
        if not os.path.exists(os.path.dirname(path)):
            os.makedirs(os.path.dirname(path))
        LOG.debug('Starting download from %s to %s (%s bytes)' % (url, path, r.headers.get('content-length')))
        with open(path, 'wb') as f:
            for chunk in r.iter_content(DOWNLOAD_CHUNK_SIZE):
                total += len(chunk)
                if chunk:  
                    f.write(chunk)
                    LOG.debug('Writing %s bytes (total %s) to %s' % (len(chunk), total, path))
                else:
                    LOG.debug('Empty chunk %s (total %s) from %s' % (chunk, total, url))
            f.flush()
            os.fsync(f)
    finally:
        LOG.debug('Done downloading %s, response code %s' % (url, r.status_code))
        r.close()
        s.close()
def parse_chunked_data(data):