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

2 files changed, 22 insertions, 0 deletions

diff --git a/app/policies/preview_card_policy.rb b/app/policies/preview_card_policy.rb
new file mode 100644
index 000000000..4f485d7fc
--- /dev/null
+++ b/app/policies/preview_card_policy.rb
@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+class PreviewCardPolicy < ApplicationPolicy
+  def index?
+    staff?
+  end
+
+  def update?
+    staff?
+  end
+end
diff --git a/app/policies/preview_card_provider_policy.rb b/app/policies/preview_card_provider_policy.rb
new file mode 100644
index 000000000..598d54a5e
--- /dev/null
+++ b/app/policies/preview_card_provider_policy.rb
@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+class PreviewCardProviderPolicy < ApplicationPolicy
+  def index?
+    staff?
+  end
+
+  def update?
+    staff?
+  end
+end