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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headers = mock_aws_request_headers()
    headers['X-Amz-Target'] = 'DynamoDB_20120810.GetItem'
    new_item = make_http_request(url=config.TEST_DYNAMODB_URL,
        method='POST', data=json.dumps(request), headers=headers)
    new_item = json.loads(new_item.text)
    return new_item
def create_dynamodb_table(table_name, partition_key, env=None, stream_view_type=None):
    """Utility method to create a DynamoDB table"""
    dynamodb = connect_to_service('dynamodb', env=env, client=True)
    stream_spec = {'StreamEnabled': False}
    key_schema = [{
        'AttributeName': partition_key,
        'KeyType': 'HASH'
    }]
    attr_defs = [{
        'AttributeName': partition_key,
        'AttributeType': 'S'
    }]
    if stream_view_type is not None:
        stream_spec = {
            'StreamEnabled': True,