feat(whitby): Configure initial Keycloak setup

Trialing this as an alternative to CAS that is a little easier to
configure and can help us delegate authentication to other OIDC
services.

Change-Id: Iad63724d349334910af8fed0b148e4ba428f796b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/4608
Tested-by: BuildkiteCI
Autosubmit: tazjin <mail@tazj.in>
Reviewed-by: lukegb <lukegb@tvl.fyi>

ops/modules/www/auth.tvl.fyi.nix

@@ -0,0 +1,24 @@
+{ config, ... }:
+
+{
+  imports = [
+    ./base.nix
+  ];
+
+  config = {
+    services.nginx.virtualHosts."auth.tvl.fyi" = {
+      serverName = "auth.tvl.fyi";
+      enableACME = true;
+      forceSSL = true;
+
+      extraConfig = ''
+        location / {
+          proxy_pass http://localhost:${config.services.keycloak.httpPort};
+          proxy_set_header X-Forwarded-For $remote_addr;
+          proxy_set_header X-Forwarded-Proto https;
+          proxy_set_header Host $host;
+        }
+      '';
+    };
+  };
+}