Support URI Auth

**Is your feature request related to a problem? Please describe.**
For some applications I want to login with URI only because they don't support custom headers. I thought it would be possible as I read the docs (https://docs.goauthentik.io/docs/add-secure-apps/providers/proxy/header_authentication#receiving-http-basic-authentication-authentik-20231), but somehow it doesn't work. If I sent the authentication header via [Restman](https://chromewebstore.google.com/detail/restman/ihgpcfpkpmdcghlnaofdmjkoemnlijdi) it works correctly so I don't think my traefik filters something. (other apps with http_basic auth work)

**Describe the solution you'd like**
Support something like https://username:password@domain.com (or maybe https://username:app_password@domain.com) and for token https://domain.com/?ak_token=token (the original would be "?access_token=", but I think this would create some collisions with the applications behind authentik.

**Additional context**

https://github.com/goauthentik/authentik/discussions/12489