Allow automatic instance redirect to be turned off

Instead the "switch invidious instance" link would bring users to
redirect.invidious.io

src/invidious/routes/misc.cr

@@ -37,8 +37,13 @@ class Invidious::Routes::Misc < Invidious::Routes::BaseRoute
   end
 
   def cross_instance_redirect(env)
-    instance_url = fetch_random_instance
     referer = get_referer(env)
+
+    if !env.get("preferences").as(Preferences).automatic_instance_redirect
+      return env.redirect("https://redirect.invidious.io#{referer}")
+    end
+
+    instance_url = fetch_random_instance
     env.redirect "https://#{instance_url}#{referer}"
   end
 end

src/invidious/routes/preferences.cr

@@ -92,6 +92,10 @@ class Invidious::Routes::PreferencesRoute < Invidious::Routes::BaseRoute
       end
     end
 
+    automatic_instance_redirect = env.params.body["automatic_instance_redirect"]?.try &.as(String)
+    automatic_instance_redirect ||= "off"
+    automatic_instance_redirect = automatic_instance_redirect == "on"
+
     locale = env.params.body["locale"]?.try &.as(String)
     locale ||= CONFIG.default_user_preferences.locale
 
@@ -141,6 +145,7 @@ class Invidious::Routes::PreferencesRoute < Invidious::Routes::BaseRoute
       quality_dash:           quality_dash,
       default_home:           default_home,
       feed_menu:              feed_menu,
+      automatic_instance_redirect: automatic_instance_redirect,
       related_videos:         related_videos,
       sort:                   sort,
       speed:                  speed,