FIX: Validate tags parameter of TopicQuery (#19830)

Recently, we have seen some errors related to invalid tags value being
passed to TopicQuery.

lib/topic_query.rb

@@ -15,10 +15,15 @@ class TopicQuery
     @validators ||=
       begin
         int = lambda { |x| Integer === x || (String === x && x.match?(/^-?[0-9]+$/)) }
-
         zero_up_to_max_int = lambda { |x| int.call(x) && x.to_i.between?(0, PG_MAX_INT) }
+        array_or_string = lambda { |x| Array === x || String === x }
 
-        { max_posts: zero_up_to_max_int, min_posts: zero_up_to_max_int, page: zero_up_to_max_int }
+        {
+          max_posts: zero_up_to_max_int,
+          min_posts: zero_up_to_max_int,
+          page: zero_up_to_max_int,
+          tags: array_or_string,
+        }
       end
   end
 

spec/requests/list_controller_spec.rb

@@ -30,6 +30,9 @@ RSpec.describe ListController do
 
       get "/latest?page=1111111111111111111111111111111111111111"
       expect(response.status).to eq(400)
+
+      get "/latest?tags[1]=hello"
+      expect(response.status).to eq(400)
     end
 
     it "returns 200 for legit requests" do
@@ -59,6 +62,9 @@ RSpec.describe ListController do
 
       get "/latest.json?topic_ids=14583%2C14584"
       expect(response.status).to eq(200)
+
+      get "/latest?tags[]=hello"
+      expect(response.status).to eq(200)
     end
 
     (Discourse.anonymous_filters - [:categories]).each do |filter|