fix shopkeeper deletion FK violation on item_tags

Shopkeeper deletion (DELETE /shopkeeper_auth) failed with
ActiveRecord::InvalidForeignKey because item_tags had RESTRICT foreign
keys on completed_by_id and created_by_id. Changed these 2 FK
constraints to ON DELETE SET NULL at both DB and model level so
item_tags are preserved with nullified shopkeeper references.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: dadachi

app/models/shopkeeper.rb

@@ -10,8 +10,8 @@ class Shopkeeper < ApplicationRecord
   has_many :shops, through: :accounts
   has_many :item_tags, through: :shops
   has_many :created_shops, class_name: "Shop", foreign_key: :created_by_id, inverse_of: :created_by
-  has_many :created_item_tags, class_name: "ItemTag", foreign_key: :created_by_id, inverse_of: :created_by
-  has_many :completed_item_tags, class_name: "ItemTag", foreign_key: :completed_by_id, inverse_of: :completed_by
+  has_many :created_item_tags, class_name: "ItemTag", foreign_key: :created_by_id, inverse_of: :created_by, dependent: :nullify
+  has_many :completed_item_tags, class_name: "ItemTag", foreign_key: :completed_by_id, inverse_of: :completed_by, dependent: :nullify
 
   attribute :token, :string
   attribute :client, :string

db/migrate/20260409072237_change_shopkeeper_foreign_keys_to_nullify_on_delete.rb

@@ -0,0 +1,17 @@
+class ChangeShopkeeperForeignKeysToNullifyOnDelete < ActiveRecord::Migration[8.1]
+  def up
+    remove_foreign_key :item_tags, column: :completed_by_id
+    remove_foreign_key :item_tags, column: :created_by_id
+
+    add_foreign_key :item_tags, :shopkeepers, column: :completed_by_id, on_delete: :nullify
+    add_foreign_key :item_tags, :shopkeepers, column: :created_by_id, on_delete: :nullify
+  end
+
+  def down
+    remove_foreign_key :item_tags, column: :completed_by_id
+    remove_foreign_key :item_tags, column: :created_by_id
+
+    add_foreign_key :item_tags, :shopkeepers, column: :completed_by_id
+    add_foreign_key :item_tags, :shopkeepers, column: :created_by_id
+  end
+end

db/schema.rb

@@ -30,6 +30,21 @@ class ShopkeeperAuth::RegistrationsControllerTest < ActionDispatch::IntegrationT
     end
   end
 
+  test "delete current shopkeeper with item_tags" do
+    shopkeeper.create_default_account
+    account = shopkeeper.accounts.first
+
+    ActsAsTenant.with_tenant(account) do
+      shop = account.shops.create!(name: "Test Shop", created_by: shopkeeper)
+      shop.item_tags.create!(queue_number: "A1", account: account, completed_by: shopkeeper)
+    end
+
+    assert_difference "Shopkeeper.count", -1 do
+      delete shopkeeper_registration_url, headers: shopkeeper.create_new_auth_token
+      assert_response :success
+    end
+  end
+
   def shopkeeper
     @shopkeeper ||= shopkeepers(:one)
   end

test/controllers/shopkeeper_auth/registrations_controller_test.rb

@@ -213,4 +213,59 @@ class ShopkeeperTest < ActiveSupport::TestCase
       shopkeeper.destroy
     end
   end
+
+  test "should nullify item_tags references on destroy" do
+    shopkeeper = shopkeepers(:one)
+    shopkeeper.create_default_account
+    other_shopkeeper = shopkeepers(:two)
+    other_shopkeeper.create_default_account
+    other_account = other_shopkeeper.accounts.first
+
+    item_tag = ActsAsTenant.with_tenant(other_account) do
+      shop = other_account.shops.create!(name: "Other Shop", created_by: other_shopkeeper)
+      shop.item_tags.create!(
+        queue_number: "A1",
+        account: other_account,
+        completed_by: shopkeeper
+      )
+    end
+
+    ActsAsTenant.without_tenant do
+      shopkeeper.destroy
+    end
+
+    ActsAsTenant.with_tenant(other_account) do
+      item_tag.reload
+      assert_nil item_tag.completed_by_id
+      assert ItemTag.exists?(item_tag.id)
+    end
+  end
+
+  test "should successfully destroy shopkeeper with item_tags in other accounts" do
+    shopkeeper = shopkeepers(:one)
+    shopkeeper.create_default_account
+    other_shopkeeper = shopkeepers(:two)
+    other_shopkeeper.create_default_account
+    other_account = other_shopkeeper.accounts.first
+
+    item_tag = ActsAsTenant.with_tenant(other_account) do
+      shop = other_account.shops.create!(name: "Other Shop", created_by: other_shopkeeper)
+      shop.item_tags.create!(
+        queue_number: "B1",
+        account: other_account,
+        created_by: shopkeeper
+      )
+    end
+
+    ActsAsTenant.without_tenant do
+      assert_nothing_raised do
+        shopkeeper.destroy!
+      end
+    end
+
+    ActsAsTenant.with_tenant(other_account) do
+      item_tag.reload
+      assert_nil item_tag.created_by_id
+    end
+  end
 end