show count for users signed in the last 30 days on users page

app/models/user.rb

@@ -99,6 +99,8 @@ class User < ActiveRecord::Base
     :conditions => "bans.id IS NOT NULL"
   scope :idle,
     :conditions => ["lastvisit < ?", 30.minutes.ago.utc]
+  scope :lately,
+    :conditions => ["lastvisit > ?", 30.days.ago.utc]
 
   before_validation :update_password
 

app/views/users/index.html.erb

@@ -1,4 +1,5 @@
 <h1 class="title">Listing Users</h1>
+<p><%= User.lately.count %> players have signed in within the past 30 days.</p>
 
 <p>Search for users by name or Steam ID:</p>
 

db/migrate/20170702150454_add_lastvisit_index_to_users.rb

@@ -0,0 +1,5 @@
+class AddLastvisitIndexToUsers < ActiveRecord::Migration
+  def change
+    add_index :users, :lastvisit
+  end
+end