Move some Rails app services to UserManager namespace

app/controllers/admin/users_controller.rb

@@ -30,7 +30,7 @@ class Admin::UsersController < Admin::BaseController
     amount = params[:amount].to_i
     notify_user = ActiveRecord::Type::Boolean.new.cast(params[:notify_user])
 
-    CreateInvitations.call(user: @user, amount: amount, notify: notify_user)
+    UserManager::CreateInvitations.call(user: @user, amount: amount, notify: notify_user)
 
     redirect_to admin_user_path(@user.cn), flash: {
       success: "Added #{amount} invitations to #{@user.cn}'s account"

app/controllers/signup_controller.rb

@@ -96,7 +96,7 @@ class SignupController < ApplicationController
     session[:new_user] = nil
     session[:validation_error] = nil
 
-    CreateAccount.call(account: {
+    UserManager::CreateAccount.call(account: {
       username: @user.cn,
       domain: Setting.primary_domain,
       email: @user.email,