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>
```
response.headers[header_name] = query_map[param_name][0]
            if response_content_str and response_content_str.startswith('<'):
                is_bytes = isinstance(response._content, six.binary_type)
                response._content = response_content_str
                append_last_modified_headers(response=response, content=response_content_str)
                
                
                
                
                
                if method != 'GET' or not is_object_specific_request(path, headers):
                    response._content = re.sub(r'([^\?])>\n\s*<', r'\1><', response_content_str, flags=re.MULTILINE)
                
                response._content = self._update_location(response._content, bucket_name)
                
                if is_bytes:
                    response._content = to_bytes(response._content)
                
                
                
                if 'text/html' in response.headers.get('Content-Type', '') \
                        and not response_content_str.lower().startswith('<!doctype html'):
                    response.headers['Content-Type'] = 'application/xml; charset=utf-8'
                reset_content_length = True
            
            if method == 'DELETE':
                reset_content_length = True
            if reset_content_length:
                response.headers['content-length'] = len(response._content)
    def _update_location(self, content, bucket_name):