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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LOG.debug('Resource %s need not be deployed: %s' % (logical_id, resource_json))
                if resource:
                    return resource
        
        resource_json_arns_fixed = clone(json_safe(convert_objs_to_ids(resource_json)))
        set_moto_account_ids(resource_json_arns_fixed)
        
        if resource or update:
            parse_and_update_resource_orig(logical_id,
                resource_json_arns_fixed, resources_map, region_name)
        elif not resource:
            resource = parse_and_create_resource_orig(logical_id,
                resource_json_arns_fixed, resources_map, region_name)
        
        if hasattr(resource, 'region_name') and resource.region_name != region_name:
            LOG.debug('Updating incorrect region from %s to %s' % (resource.region_name, region_name))
            resource.region_name = region_name
        
        update_resource_name(resource, resource_json)
        LOG.debug('Deploying CloudFormation resource: %s' % resource_json)
        try:
            CURRENTLY_UPDATING_RESOURCES[resource_hash_key] = True
            deploy_func = template_deployer.update_resource if update else template_deployer.deploy_resource
            result = deploy_func(logical_id, resource_wrapped, stack_name=stack_name)
        finally:
            CURRENTLY_UPDATING_RESOURCES[resource_hash_key] = False
        if not should_be_created:
            
            return resource
        def find_id(resource):