🧹 Payout#destroy destroys #payments

While it may be better us to void a `Payout`, making sure we clean up
any `Payout#payments` upon `Payout#destroy` should reduce the likelihood
of data being in a sad place.

app/furniture/tobias/payment.rb

@@ -2,6 +2,8 @@ class Tobias
   class Payment < ApplicationRecord
     self.table_name = "tobias_payments"
 
+    belongs_to :payout
+
     monetize :amount_cents
   end
 end

app/furniture/tobias/payout.rb

@@ -4,7 +4,7 @@ class Payout < ApplicationRecord
 
     belongs_to :trust
     has_many :beneficiaries, through: :trust
-    has_many :payments
+    has_many :payments, inverse_of: :payout, dependent: :destroy
 
     monetize :amount_cents
 

spec/tobias/payout_spec.rb

@@ -2,7 +2,11 @@
 require_relative "factories/payout_factory"
 require_relative "factories/beneficiary_factory"
 
-RSpec.describe Tobias::Payout do
+RSpec.describe Tobias::Payout, type: :model do
+  describe "#payments" do
+    it { is_expected.to have_many(:payments).inverse_of(:payout).dependent(:destroy) }
+  end
+
   describe "#issue" do
     it "issues a Payment to each Beneficiary for their share of the #amount" do
       payout = create(:tobias_payout, amount_cents: 150_00)