OAuth: "access-token: <token>" vs. "authorization: bearer <token>"

Hi,

I am trying to use OAuth access tokens for eSIGN REST API calls. However, it seems I can only to make it work when I use header field "access-token: <token>" in the request. If I provide the access token via "authorization: bearer <token>" as per OAuth definition, then it does not seem to find the token on the request, resulting in:

{

  "code": "NO_ACCESS_TOKEN_HEADER",

  "message": "Access token header not provided"

}

I verified that using "access-token" works with Postman, to exclude any other issue related to handling the token requests.

But unfortunately, other than testing with Postman, I have no way to change the http request header from "authorization" to "access-token" on the client side 😞

Apologies if I am making some obvious mistake, but I haven't found anything using the forum search...

Kind regards,
Wolfgang