chore(email): add an observer which log the emails dispatched

app/models/email_event.rb

@@ -15,4 +15,31 @@ class EmailEvent < ApplicationRecord
   enum status: {
     dispatched: 'dispatched'
   }
+  class << self
+    def create_from_message!(message, status:)
+      message.to.each do |recipient|
+        EmailEvent.create!(
+          to: pseudonymize_email(recipient),
+          subject: message.subject,
+          processed_at: message.date,
+          method: ActionMailer::Base.delivery_methods.key(message.delivery_method.class),
+          status:
+        )
+      rescue StandardError => error
+        Sentry.capture_exception(error, extra: { subject: message.subject, status: })
+      end
+    end
+
+    def pseudonymize_email(email)
+      username, domain_name = email.split("@")
+
+      username_masked = if username.length > 3
+        username[0..1] + "*" * (username.length - 3) + username[-1]
+      else
+        "*" * username.length
+      end
+
+      "#{username_masked}@#{domain_name}"
+    end
+  end
 end

app/services/email_delivery_observer.rb

@@ -0,0 +1,7 @@
+class EmailDeliveryObserver
+  def self.delivered_email(message)
+    return if message.to.nil?
+
+    EmailEvent.create_from_message!(message, status: "dispatched")
+  end
+end

config/initializers/mail_observers.rb

@@ -0,0 +1,3 @@
+Rails.application.configure do
+  config.action_mailer.observers = ['EmailDeliveryObserver']
+end

spec/mailers/application_mailer_spec.rb

@@ -25,4 +25,20 @@ RSpec.describe ApplicationMailer, type: :mailer do
       it { expect(subject.message).not_to be_an_instance_of(ActionMailer::Base::NullMail) }
     end
   end
+
+  describe 'EmailDeliveryObserver is invoked' do
+    let(:user1) { create(:user) }
+    let(:user2) { create(:user, email: "thisisyour@email.com") }
+
+    it 'creates a new EmailEvent record with the correct information' do
+      expect { UserMailer.ask_for_merge(user1, user2.email).deliver_now }.to change { EmailEvent.count }.by(1)
+      event = EmailEvent.last
+
+      expect(event.to).to eq("th*******r@email.com")
+      expect(event.method).to eq("test")
+      expect(event.subject).to eq('Fusion de compte')
+      expect(event.processed_at).to be_within(1.second).of(Time.zone.now)
+      expect(event.status).to eq('dispatched')
+    end
+  end
 end

spec/models/email_event_spec.rb

@@ -0,0 +1,7 @@
+RSpec.describe EmailEvent, type: :model do
+  describe "#pseudonymize_email" do
+    it { expect(EmailEvent.pseudonymize_email("example@rspec.com")).to eq("ex****e@rspec.com") }
+    it { expect(EmailEvent.pseudonymize_email("exa@rspec.com")).to eq("***@rspec.com") }
+    it { expect(EmailEvent.pseudonymize_email("e@rspec.com")).to eq("*@rspec.com") }
+  end
+end