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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backend.apis[new_id] = resource
            
            
            client = aws_stack.connect_to_service('apigateway')
            resources = client.get_resources(restApiId=new_id, limit=500)['items']
            
            assert len(resource.resources) == 1
            resource.resources = {}
            for res in resources:
                res_path_part = res.get('pathPart') or res.get('path')
                child = resource.add_child(res_path_part, res.get('parentId'))
                resource.resources.pop(child.id)
                child.id = res['id']
                child.api_id = new_id
                resource.resources[child.id] = child
            resource.id = new_id
        elif isinstance(resource, apigw_models.Resource):
            api_id = props['RestApiId']
            backend.apis[api_id].resources.pop(resource.id, None)
            backend.apis[api_id].resources[new_id] = resource
            resource.id = new_id
        elif isinstance(resource, apigw_models.Deployment):
            api_id = props['RestApiId']
            backend.apis[api_id].deployments.pop(resource['id'], None)
            backend.apis[api_id].deployments[new_id] = resource
            resource['id'] = new_id
        else:
            LOG.warning('Unexpected resource type when updating ID: %s' % type(resource))
    def update_physical_resource_id(resource):
        phys_res_id = getattr(resource, 'physical_resource_id', None)