move code for bulk adding users to a group from controller to model

app/controllers/admin/groups_controller.rb

@@ -28,28 +28,7 @@ class Admin::GroupsController < Admin::AdminController
     if group.present?
       users = (params[:users] || []).map {|u| u.downcase}
       user_ids = User.where("username_lower in (:users) OR email IN (:users)", users: users).pluck(:id)
-
+      group.bulk_add(user_ids) if user_ids.present?
-      if user_ids.present?
-        Group.exec_sql("INSERT INTO group_users
-                                    (group_id, user_id, created_at, updated_at)
-                       SELECT #{group.id},
-                              u.id,
-                              CURRENT_TIMESTAMP,
-                              CURRENT_TIMESTAMP
-                       FROM users AS u
-                       WHERE u.id IN (#{user_ids.join(', ')})
-                         AND NOT EXISTS(SELECT 1 FROM group_users AS gu
-                                        WHERE gu.user_id = u.id AND
-                                              gu.group_id = #{group.id})")
-
-        if group.primary_group?
-          User.where(id: user_ids).update_all(primary_group_id: group.id)
-        end
-
-        if group.title.present?
-          User.where(id: user_ids).update_all(title: group.title)
-        end
-      end
     end
 
     render json: success_json

app/models/group.rb

@@ -335,6 +335,31 @@ class Group < ActiveRecord::Base
     self.find_by(incoming_email: Email.downcase(email))
   end
 
+  def bulk_add(user_ids)
+    if user_ids.present?
+      Group.exec_sql("INSERT INTO group_users
+                                  (group_id, user_id, created_at, updated_at)
+                     SELECT #{self.id},
+                            u.id,
+                            CURRENT_TIMESTAMP,
+                            CURRENT_TIMESTAMP
+                     FROM users AS u
+                     WHERE u.id IN (#{user_ids.join(', ')})
+                       AND NOT EXISTS(SELECT 1 FROM group_users AS gu
+                                      WHERE gu.user_id = u.id AND
+                                            gu.group_id = #{self.id})")
+
+      if self.primary_group?
+        User.where(id: user_ids).update_all(primary_group_id: self.id)
+      end
+
+      if self.title.present?
+        User.where(id: user_ids).update_all(title: self.title)
+      end
+    end
+    true
+  end
+
   protected
 
     def name_format_validator