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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resource_type = get_resource_type(resource)
    service = get_service_name(resource)
    resource_config = RESOURCE_TO_FUNCTION.get(resource_type)
    if resource_config is None:
        raise Exception('CloudFormation deployment for resource type %s not yet implemented' % resource_type)
    if ACTION_CREATE not in resource_config:
        
        return
    try:
        if resource_config[ACTION_CREATE].get('boto_client') == 'resource':
            return aws_stack.connect_to_resource(service)
        return aws_stack.connect_to_service(service)
    except Exception as e:
        LOG.warning('Unable to get client for "%s" API, skipping deployment: %s' % (service, e))
        return None
def describe_stack_resource(stack_name, logical_resource_id):
    client = aws_stack.connect_to_service('cloudformation')
    result = client.describe_stack_resource(StackName=stack_name, LogicalResourceId=logical_resource_id)
    return result['StackResourceDetail']
def retrieve_resource_details(resource_id, resource_status, resources, stack_name):
    resource = resources.get(resource_id)
    resource_id = resource_status.get('PhysicalResourceId') or resource_id
    if not resource:
        resource = {}
    resource_type = get_resource_type(resource)
    resource_props = resource.get('Properties')
    try:
        if resource_type == 'Lambda::Function':