FEATURE: Embed topics list on remote sites via Javascript API. (#8008)

This adds support for a `<d-topics-list>` tag you can embed in your site
that will be rendered as a list of discourse topics. Any attributes on
the tag will be passed as filters. For example:

`<d-topics-list discourse-url="URL" category="1234">` will filter to category 1234.

To use this feature, enable the `embed topics list` site setting. Then
on the site you want to embed, include the following javascript:

`<script
src="http://URL/javascripts/embed-topics.js"></script>`

Where `URL` is your discourse forum's URL.

Then include the `<d-topics-list discourse-url="URL">` tag in your HTML document and it will
be replaced with the list of topics.

app/controllers/list_controller.rb

@@ -1,9 +1,11 @@
 # frozen_string_literal: true
 
 require_dependency 'topic_list_responder'
+require_dependency 'topic_query_params'
 
 class ListController < ApplicationController
   include TopicListResponder
+  include TopicQueryParams
 
   skip_before_action :check_xhr
 
@@ -376,28 +378,6 @@ class ListController < ApplicationController
     end
   end
 
-  def build_topic_list_options
-    options = {}
-    params[:tags] = [params[:tag_id].parameterize] if params[:tag_id].present? && guardian.can_tag_pms?
-
-    TopicQuery.public_valid_options.each do |key|
-      if params.key?(key)
-        val = options[key] = params[key]
-        if !TopicQuery.validate?(key, val)
-          raise Discourse::InvalidParameters.new key
-        end
-      end
-    end
-
-    # hacky columns get special handling
-    options[:topic_ids] = param_to_integer_list(:topic_ids)
-    if options[:no_subcategories] == 'true'
-      options[:no_subcategories] = true
-    end
-
-    options
-  end
-
   def list_target_user
     if params[:user_id] && guardian.is_staff?
       User.find(params[:user_id].to_i)