The form POST operation to S3 accepts a `success_action_status` field which can be set to 200/201/204, see [here](https://docs.aws.amazon.com/AmazonS3/latest/API/RESTObjectPOST.html). Localstack currently handles the `success_action_redirect` field [here](https://github.com/localstack/localstack/blob/master/localstack/services/s3/s3_listener.py#L518) and so we should look into handling the `success_action_status` field too.

The 201 from AWS responds with an XML document with some fields about the object that has just been created in AWS, see below.

```
<PostResponse>
    <Location>https://s3.amazonaws.com/link-to-the-file</Location>
    <Bucket>s3-bucket</Bucket>
    <Key>development/8614bd40-691b-4668-9241-3b342c6cf429/image.jpg</Key>
    <ETag>"32-bit-tag"</ETag>
</PostResponse>
```
path = to_str(path)
        method = to_str(method)
        bucket_name = get_bucket_name(path, headers)
        
        hostname_parts = headers['host'].split('.')
        if (not bucket_name or len(bucket_name) == 0) and len(hostname_parts) > 1:
            bucket_name = hostname_parts[0]
        
        
        key = None
        if method == 'POST':
            key, redirect_url = multipart_content.find_multipart_redirect_url(data, headers)
            if key and redirect_url:
                response.status_code = 303
                response.headers['Location'] = expand_redirect_url(redirect_url, key, bucket_name)
                LOGGER.debug('S3 POST {} to {}'.format(response.status_code, response.headers['Location']))
        parsed = urlparse.urlparse(path)
        bucket_name_in_host = headers['host'].startswith(bucket_name)
        should_send_notifications = all([
            method in ('PUT', 'POST', 'DELETE'),
            '/' in path[1:] or bucket_name_in_host,
            
            
            bucket_name_in_host or (len(path[1:].split('/')) > 1 and len(path[1:].split('/')[1]) > 0),
            self.is_query_allowable(method, parsed.query)
        ])