CAPT-1863: Rake task to pull message delivery status from Notify API

lib/tasks/retrieve_notify_message_status.rake

@@ -0,0 +1,38 @@
+desc "Retrieve recent message delivery status from GOV.UK Notify API"
+task :retrieve_notify_message_status, [:number_of_days] => :environment do |t, args|
+  args.with_defaults(number_of_days: 1)
+
+  require "notifications/client"
+  client = Notifications::Client.new(ENV.fetch("NOTIFY_API_KEY"))
+
+  current_message_timestamp = Time.now
+  oldest_retained_message_timestamp = current_message_timestamp - args.number_of_days.days
+
+  messages = []
+  response = nil
+
+  while current_message_timestamp > oldest_retained_message_timestamp
+    args = {}
+    args[:older_than] = response.collection.last.id if response.present?
+
+    puts "Retrieving messages older than #{current_message_timestamp}"
+
+    response = client.get_notifications(args)
+
+    messages.push(*response.collection)
+
+    current_message_timestamp = response.collection.last.created_at
+  end
+
+  puts "Retrieved #{messages.count} messages"
+
+  CSV.open("notifications.csv", "w") do |csv|
+    csv << ["Email", "Status", "Template ID", "Sent at", "Created at", "Completed at"]
+
+    messages.each do |message|
+      csv << [message.email_address, message.status, message.template["id"], message.sent_at, message.created_at, message.completed_at]
+    end
+  end
+
+  puts "Written to notifications.csv"
+end