add db changes for edit draft invoice feature

app/models/adjusted_fee.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+class AdjustedFee < ApplicationRecord
+  belongs_to :invoice
+  belongs_to :fee, optional: true
+
+  enum fee_type: Fee::FEE_TYPES
+end

db/migrate/20231220140936_create_adjusted_fees.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+class CreateAdjustedFees < ActiveRecord::Migration[7.0]
+  def change
+    create_table :adjusted_fees, id: :uuid do |t|
+      t.references :fee, type: :uuid, null: true, index: true, foreign_key: true
+      t.references :invoice, type: :uuid, null: false, index: true, foreign_key: true
+      t.references :subscription, type: :uuid, null: true, foreign_key: true, index: true
+      t.references :charge, type: :uuid, null: true, foreign_key: true, index: true
+
+      t.string :invoice_display_name
+      t.integer :fee_type
+      t.boolean :adjusted_units, default: false, null: false
+      t.boolean :adjusted_amount, default: false, null: false
+      t.decimal :units, default: '0.0', null: false
+      t.bigint :unit_amount_cents, null: false, default: 0
+      t.jsonb :properties, null: false, default: {}
+
+      t.timestamps
+    end
+  end
+end

spec/factories/adjusted_fees.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+FactoryBot.define do
+  factory :adjusted_fee do
+    invoice
+    fee
+    charge { nil }
+    subscription
+
+    fee_type { 'subscription' }
+
+    unit_amount_cents { 200 }
+    units { 2 }
+    adjusted_amount { true }
+
+    invoice_display_name { Faker::Fantasy::Tolkien.character }
+  end
+end