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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LOG.info('Creating API resources under API Gateway "%s".' % name)
    api = client.create_rest_api(name=name, description=description)
    
    api_id = api['id']
    resources_list = client.get_resources(restApiId=api_id)
    root_res_id = resources_list['items'][0]['id']
    
    for path, methods in six.iteritems(resources):
        
        parent_id = root_res_id
        for path_part in path.split('/'):
            api_resource = client.create_resource(restApiId=api_id, parentId=parent_id, pathPart=path_part)
            parent_id = api_resource['id']
        
        for method in methods:
            client.put_method(
                restApiId=api_id,
                resourceId=api_resource['id'],
                httpMethod=method['httpMethod'],
                authorizationType=method.get('authorizationType') or 'NONE',
                apiKeyRequired=method.get('apiKeyRequired') or False
            )
            
            integrations = method['integrations']
            create_api_gateway_integrations(api_id, api_resource['id'], method,
                integrations, env=env, region_name=region_name)
    
    client.create_deployment(restApiId=api_id, stageName=stage_name)
    return api
def create_api_gateway_integrations(api_id, resource_id, method,