class Decidim::Meetings::RegistrationMailer

they join a meeting.
A custom mailer for sending notifications to users when

def add_calendar_attachment 

def add_calendar_attachment
  calendar = Icalendar::Calendar.new
  calendar.add_event(Calendar::MeetingToEvent.new(@meeting).event)
  attachments["meeting-calendar-info.ics"] = calendar.to_ical
end

def confirmation(user, meeting, registration) 

def confirmation(user, meeting, registration)
  with_user(user) do
    @user = user
    @meeting = meeting
    @registration = registration
    @organization = @meeting.organization
    @locator = Decidim::ResourceLocatorPresenter.new(@meeting)
    add_calendar_attachment
    subject = I18n.t("confirmation.subject", scope: "decidim.meetings.mailer.registration_mailer")
    mail(to: user.email, subject:)
  end
end