External service Oauthv2 API

Im using Kong to proxy requests, all good using plugins, using consumers etc. but I can only proxy external services with the token as queryparams, I add it to the request transformer.

There has to be a way to authorize it properly. And I cant understand it. Its been many days of looking in to it so I have to ask.

Most of the services im proxying use Oauthv2 and Ii need to manage through Kong.

How to approach this? I think im very wrong because i cant find any information on this. All is aimed to my api consumers. And Kong is the client in this case.