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: status_messages_controller.rb
    path of file: ./repos/open-build-service/src/api/app/controllers
    
    the code of the file until where you have to start completion: class StatusMessagesController
    
  def show; end

  def create
    status_message = StatusMessage.from_xml(validate_status_message)
    authorize status_message
    status_message.save!
    render_ok
  end

  def update
    authorize @status_message
    if @status_message.update(validate_status_message)
      render_ok
    else
      render_error message: @status_message.errors.full_messages,
                   status: 400, errorcode: 'invalid_status_message'
    end
  end