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
if headers.get('x-amz-content-sha256') == 'STREAMING-AWS4-HMAC-SHA256-PAYLOAD':
            modified_data = strip_chunk_signatures(modified_data or data)
            headers['content-length'] = headers.get('x-amz-decoded-content-length')
        
        
        if method == 'POST':
            original_data = modified_data or data
            expanded_data = multipart_content.expand_multipart_filename(original_data, headers)
            if expanded_data is not original_data:
                modified_data = expanded_data
        
        
        if method == 'PUT' and not headers.get('content-type'):
            headers['content-type'] = 'binary/octet-stream'
        
        persistence.record('s3', method, path, data, headers)
        
        query = parsed_path.query
        path = parsed_path.path
        bucket = path.split('/')[1]
        query_map = urlparse.parse_qs(query, keep_blank_values=True)
        
        append_metadata_headers(method, query_map, headers)
        if query == 'notification' or 'notification' in query_map:
            
            response = handle_notification_request(bucket, method, data)
            return response
        if query == 'cors' or 'cors' in query_map: