devise_invitable: Confirm after set password

user.rb

class User < ActiveRecord::Base
  devise :invitable, :database_authenticatable, :registerable, :recoverable, 
         :rememberable, :confirmable, :validatable, :encryptable

  # ...

  # devise confirm! method overriden
  def confirm!
    welcome_message
    super
  end

  # devise_invitable accept_invitation! method overriden
  def accept_invitation!
    self.confirm!
    super
  end

  # devise_invitable invite! method overriden
  def invite!
    super
    self.confirmed_at = nil
    self.save
  end

private

  def welcome_message
    UserMailer.welcome_message(self).deliver
  end

end