OIC REST Connection - Need to pass the Credentials in the request body

Summary:

We have a 3rd party REST service and the end point requires us to obtain a token first by calling the end point and passing the user/password into the request body. Am I right in thinking the OIC connection (which holds the same user/password as basic auth) - cannot provide the credentials to the request body ? Either we need to store insecurely in OIC lookup/parameter or use Vault?

Thanks