class Decidim::Meetings::Admin::InviteJoinMeetingMailer

an existing user.
A custom mailer for sending an invitation to join a meeting to

def invite(user, meeting, invited_by)

invited_by - The user performing the invitation.
meeting - The meeting being joined.
user - The user being invited

Send an email to an user to invite them to join a meeting. 
def invite(user, meeting, invited_by)
  with_user(user) do
    @user = user
    @meeting = meeting
    @invited_by = invited_by
    @organization = @meeting.organization
    @locator = Decidim::ResourceLocatorPresenter.new(@meeting)
    subject = I18n.t("invite.subject", scope: "decidim.meetings.mailer.invite_join_meeting_mailer")
    mail(to: user.email, subject: subject)
  end
end

def routes 

def routes
  @routes ||= Decidim::EngineRouter.main_proxy(@meeting.component)
end