Adds query for daily engaged users

app/models/user_action.rb

@@ -1,4 +1,6 @@
 class UserAction < ActiveRecord::Base
+  include DateGroupable
+
   belongs_to :user
   belongs_to :target_post, class_name: "Post"
   belongs_to :target_topic, class_name: "Topic"
@@ -119,6 +121,13 @@ SQL
 
   end
 
+  def self.count_daily_engaged_users(start_date, end_date)
+    select(:user_id).distinct
+      .where(action_type: [LIKE, NEW_TOPIC, REPLY, NEW_PRIVATE_MESSAGE])
+      .smart_group_by_date(:created_at, start_date, end_date)
+      .count
+  end
+
   def self.stream_item(action_id, guardian)
     stream(action_id: action_id, guardian: guardian).first
   end