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
bucket_name = 'test-bucket-%s' % short_uid()
        self.s3_client.create_bucket(Bucket=bucket_name)
        data = '000000000000000000000000000000'
        
        upload_file_object = BytesIO()
        with gzip.GzipFile(fileobj=upload_file_object, mode='w') as filestream:
            filestream.write(data.encode('utf-8'))
        
        self.s3_client.put_object(Bucket=bucket_name, Key='test.gz',
            ContentEncoding='gzip', Body=upload_file_object.getvalue())
        
        downloaded_object = self.s3_client.get_object(Bucket=bucket_name, Key='test.gz')
        download_file_object = BytesIO(downloaded_object['Body'].read())
        with gzip.GzipFile(fileobj=download_file_object, mode='rb') as filestream:
            downloaded_data = filestream.read().decode('utf-8')
        self.assertEqual(downloaded_data, data, '{} != {}'.format(downloaded_data, data))
    def test_set_external_hostname(self):