Add user cohorts table to admin area

This table shows the percentage of users who registered in the last
twelve months, who last signed in during or later than each of those
twelve months, by month.

It is only enabled when the usage ping is enabled, and the page also
shows pretty-printed usage ping data.

The cohorts table is generated in Ruby from some basic SQL queries,
because performing the gap-filling and running sums needed in both MySQL
and Postgres is painful.

1 files changed, 2 insertions, 0 deletions

diff --git a/config/routes/admin.rb b/config/routes/admin.rb
index 3c1c2ce2582..5b44d449b2b 100644
--- a/config/routes/admin.rb
+++ b/config/routes/admin.rb
@@ -106,6 +106,8 @@ namespace :admin do
     end
   end
 
+  resources :user_cohorts, only: :index
+
   resources :builds, only: :index do
     collection do
       post :cancel_all