nil recipient in email callback after updating to 1.5+

[clinejj]

We've been getting an issue where the recipient is nil in the after_email callback of a notification. We use deliver_later, which I realize gets called around the enqueuing of the delivery (and not explicitly after). The recipient is nil only during the after_email callback, but is present in both the database and email delivery methods.

My guess is that the removal of the @recipient instance variable in #126 here caused an issue but haven't had a chance to fully debug yet: https://github.com/excid3/noticed/pull/126/files#diff-8d74699b16f13d2f080f755ae12faee3a7cd24dd19833cf203f97bb7278db400L74-L76

We've seen this issue with 1.5.0, 1.5.1, and 1.5.2, but downgrading to 1.4.1 fixed it for us.

The rough setup of our notification classes:

class MessageNotifier
  include Sidekiq::Worker

  def perform(message_type, message_url)
    message = MessageService.find_message_by_url(message_type, message_url)
    MessageService.unreads(message_url).each do |user_id, unread_ts|
      recipient = User.find(user_id)
      next if recipient.nil?

      params = { unread_ts: unread_ts, message: message }
      UnreadMessagesNotification.with(params).deliver_later(recipient) # This is the notification call
    end
  end
end

class UnreadMessagesNotification < Noticed::Base
  deliver_by :database
  deliver_by :email, mailer: 'MessageMailer',
                     method: :unread_messages_email,
                     format: :generate_mailer_params

  after_email :mark_recipient_as_read
 
  param :unread_ts, :message

  def mark_recipient_as_read
    user_id = recipient.id # Recipient is nil here
    MessageService.mark_as_read(user_id, message, as_of: unread_ts)
  end

  def generate_mailer_params
    {
      unread_ts: unread_ts,
      message: message
    }
  end
end

[clinejj]

Some further debugging led to above PR, it appears #126 did affect before callbacks (although it's not clear to me why/how)