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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def process_apigateway_invocation(func_arn, path, payload, headers={},
        resource_path=None, method=None, path_params={},
        query_string_params={}, request_context={}):
    try:
        resource_path = resource_path or path
        event = {
            'path': path,
            'headers': dict(headers),
            'pathParameters': dict(path_params),
            'body': payload,
            'isBase64Encoded': False,
            'resource': resource_path,
            'httpMethod': method,
            'queryStringParameters': query_string_params,
            'requestContext': request_context,
            'stageVariables': {}  
        }
        return run_lambda(event=event, context={}, func_arn=func_arn)
    except Exception as e:
        LOG.warning('Unable to run Lambda function on API Gateway message: %s %s' % (e, traceback.format_exc()))
def process_sns_notification(func_arn, topic_arn, subscriptionArn, message, message_attributes, subject='',):
    try:
        event = {
            'Records': [{
                'EventSource': 'localstack:sns',
                'EventVersion': '1.0',
                'EventSubscriptionArn': subscriptionArn,
                'Sns': {
                    'Type': 'Notification',
                    'TopicArn': topic_arn,