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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integrations=[], env=None, region_name=None):
    client = connect_to_service('apigateway', env=env, region_name=region_name)
    for integration in integrations:
        req_templates = integration.get('requestTemplates') or {}
        res_templates = integration.get('responseTemplates') or {}
        success_code = integration.get('successCode') or '200'
        client_error_code = integration.get('clientErrorCode') or '400'
        server_error_code = integration.get('serverErrorCode') or '500'
        
        client.put_integration(
            restApiId=api_id,
            resourceId=resource_id,
            httpMethod=method['httpMethod'],
            integrationHttpMethod=method.get('integrationHttpMethod') or method['httpMethod'],
            type=integration['type'],
            uri=integration['uri'],
            requestTemplates=req_templates
        )
        response_configs = [
            {'pattern': '^2.*', 'code': success_code, 'res_templates': res_templates},
            {'pattern': '^4.*', 'code': client_error_code, 'res_templates': {}},
            {'pattern': '^5.*', 'code': server_error_code, 'res_templates': {}}
        ]