Moved content array walker to Category#to_json

As requested by reviewer this change moves the content array walker from the API endpoint to the Category class.

src/invidious/helpers/serialized_yt_data.cr

@@ -238,7 +238,13 @@ class Category
   def to_json(locale, json : JSON::Builder)
     json.object do
       json.field "title", self.title
-      json.field "contents", self.contents
+      json.field "contents" do
+        json.array do
+          self.contents.each do |item|
+            item.to_json(locale, json)
+          end
+        end
+      end
     end
   end
 

src/invidious/routes/api/v1/search.cr

@@ -36,13 +36,7 @@ module Invidious::Routes::API::V1::Search
     JSON.build do |json|
       json.array do
         search_results.each do |item|
-          if item.is_a?(Category)
-            item.contents.each do |cat_item|
-              cat_item.to_json(locale, json) 
-            end
-          else
-            item.to_json(locale, json)
-          end
+          item.to_json(locale, json)
         end
       end
     end