apex_web_service.make_rest_request always gives error insufficient privileges
I am trying to set up a small API with my home automation and the Oracle cloud. To do this, I want to send an HTTP request from the autonomous data warehouse to a URL and process the answer in the database. I want to use apex_web_service.make_rest_request for this, and I would like to set it up as a REST data source in Apex.
I have a home automation running on a raspberry pi, and I want to call it from the Oracle Cloud database via http(s).
What I did already: