When PUTting an S3 object to Localstack with attached Metadata, if a key contains an underscore it is replaced with a dash.

However, when the same request is performed against the real S3, the key is not modified.

Example Input:
key_with_underscores => test

Localstack Result:
key-with-underscores => test

S3 Result:
key_with_underscores => test

Localstack Version: 0.10.5

Tested using AWS v2 S3 client
keys = keys if isinstance(keys, list) else [keys]
        objects = [{'Key': k} for k in keys]
        if objects:
            self.s3_client.delete_objects(Bucket=bucket_name, Delete={'Objects': objects})
        self.s3_client.delete_bucket(Bucket=bucket_name)
    def _perform_multipart_upload(self, bucket, key, data=None, zip=False, acl=None):
        kwargs = {'ACL': acl} if acl else {}
        multipart_upload_dict = self.s3_client.create_multipart_upload(Bucket=bucket, Key=key, **kwargs)
        uploadId = multipart_upload_dict['UploadId']
        
        data = data or (5 * short_uid())
        data = to_bytes(data)
        upload_file_object = BytesIO(data)
        if zip:
            upload_file_object = BytesIO()
            with gzip.GzipFile(fileobj=upload_file_object, mode='w') as filestream:
                filestream.write(data)
        response = self.s3_client.upload_part(Bucket=bucket, Key=key,
            Body=upload_file_object, PartNumber=1, UploadId=uploadId)
        multipart_upload_parts = [{'ETag': response['ETag'], 'PartNumber': 1}]
        return self.s3_client.complete_multipart_upload(Bucket=bucket,
            Key=key, MultipartUpload={'Parts': multipart_upload_parts}, UploadId=uploadId)
    def _perform_presigned_url_upload(self, bucket, key):
        url = self.s3_client.generate_presigned_url(
            'put_object', Params={'Bucket': bucket, 'Key': key}
        )
        url = url + '&X-Amz-Credential=x&X-Amz-Signature=y'
        requests.put(url, data='something', verify=False)