This allows the setting 'authorize_login_delegation_api' to work. Basically if foreman is behind any kind of proxy using Integrated Windows Authentication or Apache and mod_authnz_ldap, CAS, Cosign, WebAuth, mod_auth_sspi, etc.., foreman should trust its authentication through REMOTE_USER on API calls too.

This covers the new, dedicated API rather than the API in the UI controllers, which was enabled in #1820.