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:
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from pympler import muppy, summary
        all_objects = muppy.get_objects()
        result = summary.summarize(all_objects)
        result = result[0:20]
        summary = '\n'.join([l for l in summary.format_(result)])
        result = '%s\n\n%s' % (summary, json.dumps(result))
        return result, 200, {'content-type': 'text/plain'}
    def create_backend_app(service):
        backend_app = moto_server.create_backend_app_orig(service)
        backend_app.add_url_rule(
            '/_stats', endpoint='_get_stats', methods=['GET'], view_func=_get_stats, strict_slashes=False)
        return backend_app
    if not hasattr(moto_server, 'create_backend_app_orig'):
        moto_server.create_backend_app_orig = moto_server.create_backend_app
        moto_server.create_backend_app = create_backend_app
def start_up(*args):
    
    apply_patches()
    
    inject_stats_endpoint()
    return moto_main(*args)
def main():
    setup_logging()
    
    canonicalize_api_names()
    
    sys.exit(start_up())
if __name__ == '__main__':
    main()