Adding user settings (model and mailer), no form yet

db/migrate/20161006213403_rails_settings_migration.rb

@@ -0,0 +1,21 @@
+MIGRATION_BASE_CLASS = if ActiveRecord::VERSION::MAJOR >= 5
+  ActiveRecord::Migration[5.0]
+else
+  ActiveRecord::Migration
+end
+
+class RailsSettingsMigration < MIGRATION_BASE_CLASS
+  def self.up
+    create_table :settings do |t|
+      t.string     :var,    :null => false
+      t.text       :value
+      t.references :target, :null => false, :polymorphic => true
+      t.timestamps :null => true
+    end
+    add_index :settings, [ :target_type, :target_id, :var ], :unique => true
+  end
+
+  def self.down
+    drop_table :settings
+  end
+end