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>
```
if should_send_notifications:
            
            if key:
                object_path = '/' + key
            elif bucket_name_in_host:
                object_path = parsed.path
            else:
                parts = parsed.path[1:].split('/', 1)
                object_path = parts[1] if parts[1][0] == '/' else '/%s' % parts[1]
            version_id = response.headers.get('x-amz-version-id', None)
            send_notifications(method, bucket_name, object_path, version_id)
        
        if method in ('PUT', 'DELETE') and ('/' not in path[1:] or len(path[1:].split('/')[1]) <= 0):
            event_type = (event_publisher.EVENT_S3_CREATE_BUCKET if method == 'PUT'
                else event_publisher.EVENT_S3_DELETE_BUCKET)
            event_publisher.fire_event(event_type, payload={'n': event_publisher.get_hash(bucket_name)})
        
        if method == 'PUT' and parsed.query == 'policy':
            response._content = ''
            response.status_code = 204
            return response
        
        if method == 'GET' and response.status_code == 404 and parsed.query != 'website':
            s3_client = aws_stack.connect_to_service('s3')
            try:
                
                s3_client.head_bucket(Bucket=bucket_name)
                website_config = s3_client.get_bucket_website(Bucket=bucket_name)
                error_doc_key = website_config.get('ErrorDocument', {}).get('Key')
                if error_doc_key: