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.

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---
        operationId: 'invokeFunction'
        parameters:
            - name: 'request'
              in: body
    """
    
    arn = func_arn(function)
    
    m = re.match('(arn:aws:lambda:.*:.*:function:[a-zA-Z0-9-_]+)(:.*)?', arn)
    if m and m.group(2):
        qualifier = m.group(2)[1:]
        arn = m.group(1)
    else:
        qualifier = request.args.get('Qualifier')
    data = request.get_data()
    if data:
        data = to_str(data)
        try:
            data = json.loads(data)
        except Exception:
            try:
                
                data = json.loads(parse_chunked_data(data))
            except Exception:
                return error_response('The payload is not JSON: %s' % data, 415,
                                      error_type='UnsupportedMediaTypeException')
    
    invocation_type = request.environ.get('HTTP_X_AMZ_INVOCATION_TYPE', 'RequestResponse')
    def _create_response(result, status_code=200):