1. Add WebhookDeliveryJob

This job is responsible for delivering a payload for one webhook event only. It allows the action to run asynchronously (and not slow down the calling process).

app/jobs/webhook_delivery_job.rb

@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+require "faraday"
+
+# Deliver a webhook payload
+# As a delayed job, it can run asynchronously and handle retries.
+class WebhookDeliveryJob < ApplicationJob
+  queue_as :default
+
+  def perform(url, event, payload)
+    body = {
+      id: job_id,
+      at: Time.zone.now.to_s,
+      event: event,
+      data: payload,
+    }
+
+    notify_endpoint(url, body)
+  end
+
+  def notify_endpoint(url, body)
+    connection = Faraday.new(
+      request: { timeout: 30 },
+      headers: {
+        'User-Agent' => 'openfoodnetwork_webhook/1.0',
+        'Content-Type' => 'application/json',
+      }
+    )
+    connection.post(url, body.to_json)
+  end
+end

spec/jobs/webhook_delivery_job_spec.rb

@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe WebhookDeliveryJob do
+  subject { WebhookDeliveryJob.new(url, event, data) }
+  let(:url) { 'https://test/endpoint' }
+  let(:event) { 'order_cycle.opened' }
+  let(:data) {
+    {
+      order_cycle_id: 123, name: "Order cycle 1", open_at: 1.minute.ago.to_s, tags: ["tag1", "tag2"]
+    }
+  }
+
+  before do
+    stub_request(:post, url)
+  end
+
+  it "sends a request to specified url" do
+    subject.perform_now
+    expect(a_request(:post, url)).to have_been_made.once
+  end
+
+  it "delivers a payload" do
+    Timecop.freeze(Time.zone.now) do
+      expected_body = {
+        id: /.+/,
+        at: Time.zone.now.to_s,
+        event: event,
+        data: data,
+      }
+
+      subject.perform_now
+      expect(a_request(:post, url).with(body: expected_body)).
+        to have_been_made.once
+    end
+  end
+
+  # To be implemented in following commits
+  pending "can't access local secrets" # see https://medium.com/in-the-weeds/all-about-paperclips-cve-2017-0889-server-side-request-forgery-ssrf-vulnerability-8cb2b1c96fe8
+
+  describe "retrying" do
+    pending "doesn't retry on internal failure"
+    pending "retries after external failure"
+    pending "stops retrying after a while"
+  end
+end