OAuth Client ID and Secret Not Received in Connect Configuration (Configuration Level OAuth)

I’ve configured a Connect configuration in DocuSign and selected “Include Configuration Level OAuth” for authentication. I have entered my Auth URL, Client ID, and Client Secret in the setup.

However, when the Connect request is sent, I only receive the grant_type and my custom parameters. The client_id and client_secret values are not included in the request payload.

How does DocuSign send the Client ID and Client Secret during the OAuth call — are they sent as headers, as part of the body, or in some other format?

How can I ensure that the Client ID and Client Secret are sent as part of the OAuth request?

Thanks in advance for your help!