Noticed

Define a notification once, deliver it to as many channels as you need, and keep a
record of it in your database for the in-app inbox.

What you get

• Delivery methods for Action Mailer, Twilio, Vonage, Slack, iOS and web push
• A notification record per recipient, for the bell icon
• Per-user delivery preferences
• Bulk delivery

Adding it

class CommentNotifier < Noticed::Event
  deliver_by :database
  deliver_by :email do |config|
    config.mailer = "CommentMailer"
  end
end

CommentNotifier.with(record: comment).deliver(engine.watchers)

Why not the SaaS

A notification service needs to know your users, their preferences, and the object
being notified about. That is three sync problems you do not have if the
notifications are a table.