Fixes Rails/UniqueValidationWithoutIndex (part of #11482)

- When you define a uniqueness validation in Active Record model,
  you also should add a unique index for the column.
- Cf. https://docs.rubocop.org/rubocop-rails/cops_rails.html#railsuniquevalidationwithoutindex
- Therefore : migration files to match DB structure and Ruby code.

.rubocop_todo.yml

@@ -63,7 +63,6 @@ Metrics/ClassLength:
     - 'app/controllers/spree/admin/payment_methods_controller.rb'
     - 'app/controllers/spree/admin/payments_controller.rb'
     - 'app/controllers/spree/admin/products_controller.rb'
-    - 'app/controllers/spree/admin/users_controller.rb'
     - 'app/controllers/spree/orders_controller.rb'
     - 'app/models/enterprise.rb'
     - 'app/models/invoice/data_presenter.rb'
@@ -149,7 +148,7 @@ Metrics/MethodLength:
     - 'lib/spree/localized_number.rb'
     - 'lib/tasks/sample_data/product_factory.rb'
 
-# Offense count: 49
+# Offense count: 47
 # Configuration parameters: CountComments, Max, CountAsOne.
 Metrics/ModuleLength:
   Exclude:
@@ -176,12 +175,10 @@ Metrics/ModuleLength:
     - 'spec/controllers/admin/order_cycles_controller_spec.rb'
     - 'spec/controllers/api/v0/order_cycles_controller_spec.rb'
     - 'spec/controllers/api/v0/orders_controller_spec.rb'
-    - 'spec/controllers/payment_gateways/stripe_controller_spec.rb'
     - 'spec/controllers/spree/admin/adjustments_controller_spec.rb'
     - 'spec/controllers/spree/admin/payment_methods_controller_spec.rb'
     - 'spec/controllers/spree/admin/variants_controller_spec.rb'
     - 'spec/lib/open_food_network/address_finder_spec.rb'
-    - 'spec/lib/open_food_network/enterprise_fee_calculator_spec.rb'
     - 'spec/lib/open_food_network/order_cycle_form_applicator_spec.rb'
     - 'spec/lib/open_food_network/order_cycle_permissions_spec.rb'
     - 'spec/lib/open_food_network/permissions_spec.rb'

db/migrate/20250214192930_add_unique_index_email_entreprise_to_customers.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+class AddUniqueIndexEmailEntrepriseToCustomers < ActiveRecord::Migration[7.0]
+  def change
+    remove_index :customers, :email, name: :index_customers_on_email
+    add_index(:customers, [:email, :enterprise_id], unique: true)
+  end
+end

db/migrate/20250214200526_add_unique_index_sender_id_and_others_to_exchanges.rb

@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+class AddUniqueIndexSenderIdAndOthersToExchanges < ActiveRecord::Migration[7.0]
+  def change
+    remove_index :exchanges, :sender_id, name: :index_exchanges_on_sender_id
+    add_index(:exchanges, [:sender_id, :order_cycle_id, :receiver_id, :incoming],
+              unique: true, name: :index_exchanges_on_sender_id)
+  end
+end

db/migrate/20250215083320_add_unique_index_variant_id_and_deleted_at_to_stock_items.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+class AddUniqueIndexVariantIdAndDeletedAtToStockItems < ActiveRecord::Migration[7.0]
+  def change
+    remove_index :spree_stock_items, :variant_id, name: :index_spree_stock_items_on_variant_id
+    add_index(:spree_stock_items, [:variant_id, :deleted_at], unique: true)
+  end
+end

db/migrate/20250215085838_add_unique_index_name_and_deleted_at_to_tax_categories.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class AddUniqueIndexNameAndDeletedAtToTaxCategories < ActiveRecord::Migration[7.0]
+  def change
+    add_index(:spree_tax_categories, [:name, :deleted_at], unique: true)
+  end
+end

db/migrate/20250215091227_add_unique_index_name_to_zones.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class AddUniqueIndexNameToZones < ActiveRecord::Migration[7.0]
+  def change
+    add_index(:spree_zones, :name, unique: true)
+  end
+end