Use last_activity_on in cohorts

app/services/cohorts_service.rb

@@ -68,24 +68,24 @@ class CohortsService
   # Get a hash that looks like:
   #
   #     {
-  #       [created_at_month, current_sign_in_at_month] => count,
-  #       [created_at_month, current_sign_in_at_month_2] => count_2,
+  #       [created_at_month, last_activity_on_month] => count,
+  #       [created_at_month, last_activity_on_month_2] => count_2,
   #       # etc.
   #     }
   #
-  # created_at_month can never be nil, but current_sign_in_at_month can (when a
+  # created_at_month can never be nil, but last_activity_on_month can (when a
   # user has never logged in, just been created). This covers the last
   # MONTHS_INCLUDED months.
   def counts_by_month
     @counts_by_month ||=
       begin
         created_at_month = column_to_date('created_at')
-        current_sign_in_at_month = column_to_date('current_sign_in_at')
+        last_activity_on_month = column_to_date('last_activity_on')
 
         User
           .where('created_at > ?', MONTHS_INCLUDED.months.ago.end_of_month)
-          .group(created_at_month, current_sign_in_at_month)
-          .reorder("#{created_at_month} ASC", "#{current_sign_in_at_month} ASC")
+          .group(created_at_month, last_activity_on_month)
+          .reorder("#{created_at_month} ASC", "#{last_activity_on_month} ASC")
           .count
       end
   end

spec/services/cohorts_service_spec.rb

@@ -11,8 +11,8 @@ describe CohortsService do
       6.times do |months_ago|
         months_ago_time = (months_ago * 2).months.ago
 
-        create(:user, created_at: months_ago_time, current_sign_in_at: Time.now)
-        create(:user, created_at: months_ago_time, current_sign_in_at: months_ago_time)
+        create(:user, created_at: months_ago_time, last_activity_on: Time.now)
+        create(:user, created_at: months_ago_time, last_activity_on: months_ago_time)
       end
 
       create(:user) # this user is inactive and belongs to the current month