db(referentiel): add a weekly cron to delete orphan referentiels

app/jobs/cron/purge_orphan_referentiels_job.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+class Cron::PurgeOrphanReferentielsJob < Cron::CronJob
+  self.schedule_expression = "every week at 4:00"
+
+  def perform
+    referentiel_ids = TypeDeChamp.pluck(:referentiel_id).compact.uniq
+
+    Referentiel.where.not(id: referentiel_ids)&.find_each(&:destroy)
+  end
+end

spec/factories/referentiel.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+FactoryBot.define do
+  factory :referentiel do
+    name { 'referentiel.csv' }
+  end
+end

spec/jobs/cron/purge_orphan_referentiels_job_spec.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+RSpec.describe Cron::PurgeOrphanReferentielsJob, type: :job do
+  let!(:used_referentiel) { create(:referentiel) }
+  let!(:orphan_referentiel) { create(:referentiel) }
+  let!(:type_de_champ) { create(:type_de_champ, referentiel_id: used_referentiel.id) }
+
+  subject(:perform_job) { described_class.perform_now }
+
+  describe '#perform' do
+    it { expect { subject }.to change(Referentiel, :count).by(-1) }
+  end
+end