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>
```
error_object = s3_client.get_object(Bucket=bucket_name, Key=error_doc_key)
                    response.status_code = 200
                    response._content = error_object['Body'].read()
                    response.headers['content-length'] = len(response._content)
            except ClientError:
                
                pass
        if response:
            reset_content_length = False
            
            append_cors_headers(bucket_name, request_method=method, request_headers=headers, response=response)
            append_last_modified_headers(response=response)
            append_list_objects_marker(method, path, data, response)
            
            
            if method == 'PUT' and ('X-Amz-Security-Token=' in path or
                    'X-Amz-Credential=' in path or 'AWSAccessKeyId=' in path):
                response._content = ''
                reset_content_length = True
            response_content_str = None
            try:
                response_content_str = to_str(response._content)
            except Exception:
                pass
            
            
            if method == 'GET':
                query_map = urlparse.parse_qs(parsed.query, keep_blank_values=True)
                for param_name, header_name in ALLOWED_HEADER_OVERRIDES.items():
                    if param_name in query_map: