At the moment referer is set in haproxy configs to resolve T326217 though we would like to remove haproxy, so let's put it in ingress-nginx configs instead.
The following annotation in the jupyterhub ingress config seems to get things working in codfw1dev:
nginx.ingress.kubernetes.io/configuration-snippet: | more_set_input_headers "REFERER: http://hub-paws-dev.codfw1dev.wmcloud.org/hub/";