invalid_client error during token exchange - clientSecret might need to be passed in request body

## Issue

Hello,

I am trying to configure the Oauth 2 flow for Whoop. The Authentication step works but hte tokenn exchange fails with the error invalid_client : Error: Client authentication failed (e.g., unknown client, no client authentication included, or unsupported authentication method).
Using postman, the flow works when the client id and secret are passed in the token request body and not as a request query parameter but I cannot seem to find the right parameters to pass in the config object to do so (if the error is even what I think).

I have looked on other issues, but can't seem to find the solution.

Thanks a lot for your time and help,

Best

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## Environment

* **Your Identity Provider**: WHOOP
* **Platform that you're experiencing the issue on**: both
* **Are you using Expo?** No

Review the OAuth configuration and token-exchange path for the WHOOP provider, focusing on how the client ID and secret are supplied. Reproduce the failure described in the issue and compare it with the working Postman request. Done means the supported configuration is identified and either the exchange succeeds with credentials in the request body or the limitation is documented.

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