refactor(ops): Split //ops/nixos into different locations

Splits //ops/nixos into:

* //ops/nixos.nix - utility functions for building systems
* //ops/machines - shared machine definitions (read by readTree)
* //ops/modules - shared NixOS modules (skipped by readTree)

This simplifies working with the configuration fixpoint in whitby, and
is overall a bit more in line with how NixOS systems in user folders
currently work.

Change-Id: I1322ec5cc76c0207c099c05d44828a3df0b3ffc1
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2931
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
Reviewed-by: glittershark <grfn@gws.fyi>

ops/modules/www/tvl.fyi.nix

@@ -0,0 +1,30 @@
+{ depot, ... }:
+
+{
+  imports = [
+    ./base.nix
+  ];
+
+  config = {
+    services.nginx.virtualHosts."tvl.fyi" = {
+      serverName = "tvl.fyi";
+      root = depot.web.tvl;
+      enableACME = true;
+      forceSSL = true;
+
+      extraConfig = ''
+        add_header Strict-Transport-Security "max-age=31536000; includeSubDomains; preload" always;
+
+        rewrite ^/builds/?$ https://buildkite.com/tvl/depot/ last;
+
+        rewrite ^/monorepo-doc/?$ https://docs.google.com/document/d/1nnyByXcH0F6GOmEezNOUa2RFelpeRpDToBLYD_CtjWE/edit?usp=sharing last;
+
+        rewrite ^/irc/?$ ircs://chat.freenode.net:6697/##tvl last;
+
+        location ~* \.(webp|woff2)$ {
+          add_header Cache-Control "public, max-age=31536000";
+        }
+      '';
+    };
+  };
+}