Make NAV honor REMOTE_USER environment variable as an alternative way of providing login/provisioning first-time users into NAV. REMOTE_USER will be set by the reverse-proxy infront of NAV (commonly Apache) via Shibboleth (populating it with the EPPN attribute)

(https://wiki.shibboleth.net/confluence/display/SHIB2/NativeSPAttributeAccess#NativeSPAttributeAccess-REMOTE_USER)