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:
👉  https://opencollective.com/localstack/donate -->
resource_id = resource_props['FunctionName'] if resource else resource_id
            return aws_stack.connect_to_service('lambda').get_function(FunctionName=resource_id)
        elif resource_type == 'Lambda::Version':
            name = resource_props['FunctionName']
            func_name = aws_stack.lambda_function_name(name)
            func_version = name.split(':')[7] if len(name.split(':')) > 7 else '$LATEST'
            versions = aws_stack.connect_to_service('lambda').list_versions_by_function(FunctionName=func_name)
            return ([v for v in versions['Versions'] if v['Version'] == func_version] or [None])[0]
        elif resource_type == 'Lambda::EventSourceMapping':
            resource_id = resource_props['FunctionName'] if resource else resource_id
            source_arn = resource_props.get('EventSourceArn')
            resource_id = resolve_refs_recursively(stack_name, resource_id, resources)
            source_arn = resolve_refs_recursively(stack_name, source_arn, resources)
            if not resource_id or not source_arn:
                raise Exception('ResourceNotFound')
            mappings = aws_stack.connect_to_service('lambda').list_event_source_mappings(
                FunctionName=resource_id, EventSourceArn=source_arn)
            mapping = list(filter(lambda m:
                m['EventSourceArn'] == source_arn and m['FunctionArn'] == aws_stack.lambda_function_arn(resource_id),
                mappings['EventSourceMappings']))
            if not mapping:
                raise Exception('ResourceNotFound')
            return mapping[0]
        elif resource_type == 'DynamoDB::Table':
            resource_id = resource_props['TableName'] if resource else resource_id
            return aws_stack.connect_to_service('dynamodb').describe_table(TableName=resource_id)
        elif resource_type == 'ApiGateway::RestApi':
            apis = aws_stack.connect_to_service('apigateway').get_rest_apis()['items']
            resource_id = resource_props['Name'] if resource else resource_id
            result = list(filter(lambda api: api['name'] == resource_id, apis))