tokenRequest
Performs a token endpoint request with the given form parameters.
Posts formParams to the token endpoint, parses the response into TokenInfo, and runs full validation via processTokenResponse (ID token, access token, device secret validation + event emission).
This is the KMP equivalent of the Android @InternalAuthFoundationApi tokenRequest method. Flow classes should call this instead of making their own HTTP calls to the token endpoint.
Return
Result.success with the validated TokenInfo, or Result.failure with:
OAuth2ClientResult.Error.OidcEndpointsNotAvailableException if endpoints cannot be resolved.
OAuth2ClientResult.Error.HttpResponseException if the server returns an error.
IdTokenValidator.Error if ID token validation fails.
Other exceptions for network or parsing failures.
Parameters
the form parameters for the token request (e.g., grant_type, client_id, etc.).
the nonce sent with the authorization request, if applicable.
the max_age sent with the authorization request, if applicable.