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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return not env or env.region == REGION_LOCAL or env.prefix == ENV_DEV
def connect_to_resource(service_name, env=None, region_name=None, endpoint_url=None):
    """
    Generic method to obtain an AWS service resource using boto3, based on environment, region, or custom endpoint_url.
    """
    return connect_to_service(service_name, client=False, env=env, region_name=region_name, endpoint_url=endpoint_url)
def get_boto3_credentials():
    global INITIAL_BOTO3_SESSION
    if CUSTOM_BOTO3_SESSION:
        return CUSTOM_BOTO3_SESSION.get_credentials()
    if not INITIAL_BOTO3_SESSION:
        INITIAL_BOTO3_SESSION = boto3.session.Session()
    return INITIAL_BOTO3_SESSION.get_credentials()
def get_boto3_session():
    if CUSTOM_BOTO3_SESSION:
        return CUSTOM_BOTO3_SESSION
    if CREATE_NEW_SESSION_PER_BOTO3_CONNECTION:
        return boto3.session.Session()
    
    return boto3
def get_region():