This config means: hey Grafana - don’t use your auth, but trust what you will receive in the X-Authenticated-User header (e.g. if there is admin, so it is admin user, etc). You must ensure that the request was authenticated/authorized before it reaches Grafana (you set up auth proxy in front of Grafana - you likes OIDC, so you will set up some OIDC auth proxy) - Grafana is just a blind app, which follows/trusts the header value in this setup.
