SimpleJson datasource authorization header not being sent

I’m using Grafana v8.0.6 and I’m trying to set up a SimpleJson datsource, I’ve checked the basic authorization flag and I’ve configured the username and password for the authorization.

When I press “Save and test” I get a request in my backend for the webservice I’ve set up to process this datasource’s petitions but I don’t get any authorization header.

Is there anything else I’m supposed to configure in the datasource?