Create Job and Service for sending the chaser

This outlines a single test for sending the chaser email. It also creates the relevant Job and Service.

When users haven't attended a workshop they were invited to in the last three months _and_ haven't already been chased, they'll be sent a follow up email

Signed-off-by: jonathan.kerr <3410350+jonodrew@users.noreply.github.com>

Author: jonodrew

app/jobs/send_three_month_email_job.rb

@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+class SendThreeMonthEmailJob < ApplicationJob
+  queue_as :default
+
+  def perform
+    ThreeMonthEmailService.send_chaser
+  end
+end

app/services/three_month_email_service.rb

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+# frozen_string_literal: true
+
+class ThreeMonthEmailService
+  def self.send_chaser
+    members = Member.joins(:workshop_invitations)
+                    .left_joins(:member_email_deliveries)
+                    .where(workshop_invitations: { attended: false })
+                    .where("workshop_invitations.created_at >= ?", 3.months.ago.beginning_of_day)
+                    .where(member_email_deliveries: { id: nil })
+                    .distinct
+    return if members.empty?
+    members.each do |member|
+      MemberMailer.with(member: member).chaser.deliver_later
+    end
+  end
+end

spec/fabricators/member_email_delivery_fabricator.rb

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+Fabricator(:member_email_delivery) do
+  member(fabricator: :member)
+  subject("Chaser")
+  body("Lorem ipsum")
+  to(["test_email@address"])
+end

spec/services/three_month_email_service_spec.rb

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+RSpec.describe ThreeMonthEmailService, type: :service do
+  describe "#send_chaser" do
+    subject(:call) { described_class.send_chaser }
+
+    let!(:eligible_member)      { Fabricate(:member) }
+    let!(:emailed_member)       { Fabricate(:member) }
+    let!(:old_invite_member)    { Fabricate(:member) }
+
+    before do
+      # Eligible: recent invite, no email delivery
+      Fabricate(
+        :workshop_invitation,
+        member: eligible_member,
+        created_at: 3.months.ago,
+        attended: false
+      )
+
+      # Already emailed: recent invite, but has email delivery
+      Fabricate(
+        :workshop_invitation,
+        member: emailed_member,
+        created_at: 2.months.ago
+      )
+      Fabricate(
+        :member_email_delivery,
+        member: emailed_member
+      )
+
+      # Old invite: more than 3 months ago
+      Fabricate(
+        :workshop_invitation,
+        member: old_invite_member,
+        created_at: 4.months.ago
+      )
+    end
+
+    it "enqueues chaser emails only for eligible members" do
+      expect {
+        call
+      }.to have_enqueued_mail(MemberMailer, :chaser).once
+    end
+  end
+end