Issue 5402 - Extract language and region from ?fb_locale

modules/web/templates/site.conf.erb

 root /var/www/<%= @vhost %>;
 index index;
 default_type text/html;
 charset utf-8;
 
 set $index_page "index";
 
 <% if @custom_config %>
   <%= @custom_config %>
 <% end %>
 
 location /
 {
   expires 1d;
 
   # Match Accept-Language header against available languages
 
   set $preferredLang en;
   set $preferredRegion "";
   if ($http_accept_language ~ ^(\w\w)\b)
   {
     set $preferredLang $1;
   }
   if ($http_accept_language ~ ^\w\w-(\w\w)\b)
   {
     set $preferredRegion $1;
   }
 
+  if ($arg_fb_locale ~ ^(\w\w)_(\w\w)$)
+  {
+    set $preferredLang $1;
+    set $preferredRegion $2;
+  }
+
   # Redirect canonical URLs to language-specific versions
 
   if (-e "$document_root/${preferredLang}_$preferredRegion$uri")
   {
     rewrite ^(.*) /${preferredLang}_$preferredRegion$1 last;
   }
   if (-e "$document_root/$preferredLang$uri")
   {
     rewrite ^(.*) /$preferredLang$1 last;
   }
@@ skipping 11 matching lines @@
 
 <% if @multiplexer_locations %>
   <% @multiplexer_locations.each do |location| %>
   location <%= location %>
   {
     fastcgi_pass unix:/tmp/multiplexer-fastcgi.sock;
     include /etc/nginx/fastcgi_params;
   }
   <% end %>
 <% end %>