Remove XFrameOptionsMiddleware
The XFrameOptionsMiddleware middleware sets the X-Frame-Options header, which we already do in our nginx instance.
Previous behaviour
$ curl -I https://thalia.nu/
...
x-frame-options: SAMEORIGIN
...
x-frame-options: SAMEORIGIN
...New behaviour
$ curl -I https://thalia.nu/
...
x-frame-options: SAMEORIGIN
...Edited by Ghost User