You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: letter_with_invoice.rb
    path of file: ./repos/hitobito/app/models/message
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

#  Copyright (c) 2012-2022, Die Mitte Schweiz. This file is part of
    
  def build_invoice_for(receiver)
    invoice.tap do |invoice|
      invoice.recipient = receiver
      invoice.send(:set_recipient_fields!)
      raise 'invoice invalid' unless invoice.valid?
    end
  end