[cloud] add sameorigin for X-Frame-Options
The move to traefik 2 now set for all services the X-FRAME-OPTIONS
to none
. It is now raising a warning on Nextcloud that it should be set to sameorigin
(cf. https://docs.nextcloud.com/server/17/admin_manual/installation/harden_server.html?highlight=sameorigin#serve-security-related-headers-by-the-web-server)
This MR is setting the header to sameorigin
for Nextcloud through labels.