Hey there and thanks for this library.

It seems that there is a problem with the accept headers that are set in a request and the expected content type.
The library expects a token in json and should therefore set the Accept: application/json header rather than RawHeader("Accept", "*/*").
Github for example will send a request containing only access_token=e72e16c7e42f292c6912e7710c838347ae178b4a&token_type=bearer, resulting in an unmarshalling error: (akka.http.scaladsl.unmarshalling.Unmarshaller$UnsupportedContentTypeException: Unsupported Content-Type, supported: application/json

Or am I missing something?

Kind regards