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>
```
def sub(match):
            
            bucket_name = normalize_bucket_name(match.group(1))
            return '/%s%s' % (bucket_name, match.group(2) or '')
        path_new = re.sub(r'/([^?/]+)([?/].*)?', sub, path)
        if path == path_new:
            return
        url = '%s://%s:%s%s' % (get_service_protocol(), constants.LOCALHOST,
            constants.DEFAULT_PORT_S3_BACKEND, path_new)
        return url
    def return_response(self, method, path, data, headers, response):