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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'Subject': subject,
                    'Message': message,
                    'Timestamp': timestamp(format=TIMESTAMP_FORMAT_MILLIS),
                    'MessageAttributes': message_attributes
                }
            }]
        }
        return run_lambda(event=event, context={}, func_arn=func_arn, asynchronous=True)
    except Exception as e:
        LOG.warning('Unable to run Lambda function on SNS message: %s %s' % (e, traceback.format_exc()))
def process_kinesis_records(records, stream_name):
    
    try:
        stream_arn = aws_stack.kinesis_stream_arn(stream_name)
        sources = get_event_sources(source_arn=stream_arn)
        for source in sources:
            arn = source['FunctionArn']
            event = {
                'Records': []
            }
            for rec in records:
                event['Records'].append({
                    'eventID': 'shardId-000000000000:{0}'.format(rec['sequenceNumber']),
                    'eventSourceARN': stream_arn,
                    'kinesis': rec
                })
            run_lambda(event=event, context={}, func_arn=arn)
    except Exception as e:
        LOG.warning('Unable to run Lambda function on Kinesis records: %s %s' % (e, traceback.format_exc()))
def process_sqs_message(message_body, message_attributes, queue_name, region_name=None):