Add trending links (#16917)

* Add trending links

* Add overriding specific links trendability

* Add link type to preview cards and only trend articles

Change trends review notifications from being sent every 5 minutes to being sent every 2 hours

Change threshold from 5 unique accounts to 15 unique accounts

* Fix tests

spec/controllers/api/v1/trends/tags_controller_spec.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe Api::V1::Trends::TagsController, type: :controller do
+  render_views
+
+  describe 'GET #index' do
+    before do
+      trending_tags = double()
+
+      allow(trending_tags).to receive(:get).and_return(Fabricate.times(10, :tag))
+      allow(Trends).to receive(:tags).and_return(trending_tags)
+
+      get :index
+    end
+
+    it 'returns http success' do
+      expect(response).to have_http_status(200)
+    end
+  end
+end

spec/controllers/api/v1/trends_controller_spec.rb

@@ -1,18 +0,0 @@
-# frozen_string_literal: true
-
-require 'rails_helper'
-
-RSpec.describe Api::V1::TrendsController, type: :controller do
-  render_views
-
-  describe 'GET #index' do
-    before do
-      allow(TrendingTags).to receive(:get).and_return(Fabricate.times(10, :tag))
-      get :index
-    end
-
-    it 'returns http success' do
-      expect(response).to have_http_status(200)
-    end
-  end
-end