Add deleted_at for User

Do not remove the user from the database. Mark as deleted instead.

db/migrate/20160217115252_add_deleted_at_to_user.rb

@@ -0,0 +1,5 @@
+class AddDeletedAtToUser < ActiveRecord::Migration
+  def change
+    add_column :users, :deleted_at, :datetime
+  end
+end

db/schema.rb

@@ -346,6 +346,7 @@ ActiveRecord::Schema.define(version: 20160217194036) do
     t.datetime "reset_password_expires"
     t.datetime "last_login"
     t.datetime "last_activity"
+    t.datetime "deleted_at"
   end
 
   add_index "users", ["email"], name: "index_users_on_email", unique: true, using: :btree