feat(web/blog): Add Nix-based static blog generator

This introduces a derivation which builds an instance of nginx
statically serving my blog posts, though as of now no indexes are
being generated and no XML feed is available.

This is just the initial draft of this setup and not yet what shall be
yielded in the end.

web/blog/nginx.nix

@@ -0,0 +1,68 @@
+# This file creates an nginx server that serves the blog on port 8080.
+#
+# It's not intended to be the user-facing nginx.
+{ pkgs, lib, posts, renderedBlog, ... }:
+
+let
+  inherit (builtins) hasAttr filter map;
+  inherit (pkgs.third_party) writeText writeShellScriptBin nginx;
+
+  oldRedirects = lib.concatStringsSep "\n" (map (post: ''
+    location ~* ^(en)?/${post.oldKey} {
+      # TODO(tazjin): 301 once this works
+      return 302 /${post.key};
+    }
+  '') (filter (hasAttr "oldKey") posts));
+
+  config = writeText "blog-nginx.conf" ''
+    daemon off;
+    worker_processes 1;
+    error_log stderr;
+    pid /tmp/nginx-tazblog.pid;
+
+    events {
+      worker_connections  1024;
+    }
+
+    http {
+      include ${nginx}/conf/mime.types;
+      fastcgi_temp_path /tmp/nginx-tazblog;
+      uwsgi_temp_path /tmp/nginx-tazblog;
+      scgi_temp_path /tmp/nginx-tazblog;
+      client_body_temp_path /tmp/nginx-tazblog;
+      proxy_temp_path /tmp/nginx-tazblog;
+      sendfile on;
+
+      # Logging is handled by the primary nginx server
+      access_log off;
+
+      server {
+        listen 8080 default_server;
+        root ${renderedBlog};
+
+        location /static {
+          alias ${./static}/;
+        }
+
+        ${oldRedirects}
+
+        location / {
+          if ($request_uri ~ ^/(.*)\.html$) {
+            return 302 /$1;
+          }
+
+          try_files $uri $uri.html $uri/ =404;
+        }
+      }
+    }
+  '';
+in writeShellScriptBin "tazblog" ''
+  if [[ -v CONTAINER_SETUP ]]; then
+    cd /run
+    echo 'nogroup:x:30000:nobody' >> /etc/group
+    echo 'nobody:x:30000:30000:nobody:/tmp:/bin/bash' >> /etc/passwd
+  fi
+
+  mkdir -p /tmp/nginx-tazblog
+  exec ${pkgs.third_party.nginx}/bin/nginx -c ${config}
+''