feat(dunning): validate dunning campaign has at least one threshold

👉 https://getlago.canny.io/feature-requests/p/set-up-payment-retry-logic

👉 https://getlago.canny.io/feature-requests/p/send-reminders-for-overdue-invoices

 ## Context

We want to automate dunning process so that our users don't have to look
at each customer to maximize their chances of being paid retrying
payments of overdue balances and sending email reminders.

We're first automating the overdue balance payment request, before
looking at individual invoices.

 ## Description

This change introduces validation to ensure dunning campaign at least
has one threshold

app/models/dunning_campaign.rb

@@ -16,12 +16,20 @@ class DunningCampaign < ApplicationRecord
   validates :days_between_attempts, numericality: {greater_than: 0}
   validates :max_attempts, numericality: {greater_than: 0}
   validates :code, uniqueness: {scope: :organization_id}
+  validate :must_have_at_least_one_threshold
 
   scope :applied_to_organization, -> { where(applied_to_organization: true) }
 
   def self.ransackable_attributes(_auth_object = nil)
     %w[name code]
   end
+
+  private
+
+  def must_have_at_least_one_threshold
+    errors.add(:thresholds, "must have at least one") if thresholds.empty?
+  end
+
 end
 
 # == Schema Information

spec/factories/dunning_campaigns.rb

@@ -8,5 +8,9 @@
     days_between_attempts { Faker::Number.number(digits: 2) }
     max_attempts { Faker::Number.number(digits: 2) }
     applied_to_organization { false }
+
+    after(:build) do |dunning_campaign|
+      dunning_campaign.thresholds << build(:dunning_campaign_threshold, dunning_campaign: dunning_campaign) if dunning_campaign.thresholds.empty?
+    end
   end
 end

spec/models/dunning_campaign_spec.rb

@@ -17,4 +17,11 @@
   it { is_expected.to validate_numericality_of(:max_attempts).is_greater_than(0) }
 
   it { is_expected.to validate_uniqueness_of(:code).scoped_to(:organization_id) }
+
+  it "is invalid without any thresholds" do
+    dunning_campaign = DunningCampaign.new
+
+    expect(dunning_campaign).not_to be_valid
+    expect(dunning_campaign.errors[:thresholds]).to include("must have at least one")
+  end
 end

spec/services/dunning_campaigns/create_service_spec.rb

@@ -51,5 +51,19 @@
         end
       end
     end
+
+    context "without thresholds" do
+      let(:thresholds) { [] }
+
+      it "returns an error" do
+        result = create_service.call
+
+        aggregate_failures do
+          expect(result).not_to be_success
+          expect(result.error).to be_a(BaseService::ValidationFailure)
+          expect(result.error.messages[:thresholds]).to eq(["must have at least one"])
+        end
+      end
+    end
   end
 end