foodsoft/plugins/wiki/lib/foodsoft_wiki/mailer.rb

module FoodsoftWiki
  module Mailer
    def self.included(base) # :nodoc:
      base.class_eval do
        # modify user presentation link to writing a message for the user
        def additonal_welcome_text(_user)
          return unless FoodsoftWiki.enabled? && (page = Page.welcome_mail)

          page.body
        end
      end
    end
  end
end

# modify existing helper
ActiveSupport.on_load(:after_initialize) do
  Mailer.include FoodsoftWiki::Mailer
end