Add popular-enabled option

This is similar to the removed `top-enabled` option but for the Popular feed.
The instance needs to be restarted if the feed was enabled.

Editing admin options on the preferences page is also fixed.

The handling of the feed pages now only happens in a single place.

Instead of redirecting:
  - The Top feed now displays a message that it was removed from Invidious.
  - The Popular feed now displays a message that it was disabled if it was.

src/invidious/routes/home.cr

@@ -5,30 +5,24 @@ class Invidious::Routes::Home < Invidious::Routes::BaseRoute
     user = env.get? "user"
 
     case preferences.default_home
-    when ""
-      templated "empty"
     when "Popular"
-      templated "popular"
+      env.redirect "/feed/popular"
     when "Trending"
       env.redirect "/feed/trending"
     when "Subscriptions"
       if user
         env.redirect "/feed/subscriptions"
       else
-        templated "popular"
+        env.redirect "/feed/popular"
       end
     when "Playlists"
       if user
         env.redirect "/view_all_playlists"
       else
-        templated "popular"
+        env.redirect "/feed/popular"
       end
     else
       templated "empty"
     end
   end
-
-  private def popular_videos
-    Jobs::PullPopularVideosJob::POPULAR_VIDEOS.get
-  end
 end

src/invidious/routes/user_preferences.cr

@@ -154,6 +154,10 @@ class Invidious::Routes::UserPreferences < Invidious::Routes::BaseRoute
         end
         config.default_user_preferences.feed_menu = admin_feed_menu
 
+        popular_enabled = env.params.body["popular_enabled"]?.try &.as(String)
+        popular_enabled ||= "off"
+        config.popular_enabled = popular_enabled == "on"
+
         captcha_enabled = env.params.body["captcha_enabled"]?.try &.as(String)
         captcha_enabled ||= "off"
         config.captcha_enabled = captcha_enabled == "on"