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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return json.loads(json.dumps(item))
def remove_non_ascii(text):
    
    text = text.decode('utf-8', CODEC_HANDLER_UNDERSCORE)
    
    text = text.encode('ascii', CODEC_HANDLER_UNDERSCORE)
    return text
class NetrcBypassAuth(requests.auth.AuthBase):
    def __call__(self, r):
        return r
class _RequestsSafe(type):
    """ Wrapper around requests library, which can prevent it from verifying
    SSL certificates or reading credentials from ~/.netrc file """
    verify_ssl = True
    def __getattr__(self, name):
        method = requests.__dict__.get(name.lower())
        if not method:
            return method
        def _wrapper(*args, **kwargs):
            if 'auth' not in kwargs:
                kwargs['auth'] = NetrcBypassAuth()
            if not self.verify_ssl and args[0].startswith('https://') and 'verify' not in kwargs:
                kwargs['verify'] = False
            return method(*args, **kwargs)
        return _wrapper
class safe_requests(with_metaclass(_RequestsSafe)):