Refactor and improve invoices

- `runner 'Invoice.cancel_overdue_invoices'` in `schedule.rb` is
changed to `rake 'invoices:cancel_overdue'`.
- `invoices.payment_term` database column is removed and its value is
hardcoded in UI.
- `invoices.paid_at` is removed as unused
- `invoices.due_date` column's type is now `date`.
- `Invoice#invoice_items` renamed to `Invoice#items` and `Invoice`
interface to get a list of items is unified.
- Default date format in UI.
- Default translations are used.
- Tests improved.
- Specs converted to tests and removed along with factories.
- Database structure improved.

test/system/admin_area/invoices_test.rb

@@ -0,0 +1,20 @@
+require 'test_helper'
+
+class AdminAreaInvoicesTest < ApplicationSystemTestCase
+  setup do
+    sign_in users(:admin)
+    @invoice = invoices(:one)
+  end
+
+  def test_cancels_an_invoice
+    @invoice.account_activity = nil
+    assert @invoice.cancellable?
+
+    visit admin_invoice_url(@invoice)
+    click_on 'Cancel'
+    @invoice.reload
+
+    assert @invoice.cancelled?
+    assert_text 'Invoice has been cancelled'
+  end
+end

test/system/registrar_area/invoices/list_test.rb

@@ -1,12 +1,12 @@
 require 'test_helper'
 
 class ListInvoicesTest < ApplicationSystemTestCase
-  def setup
-    super
-
+  setup do
     @user = users(:api_bestnames)
-    @registrar_invoices = @user.registrar.invoices
     sign_in @user
+
+    @invoice = invoices(:one)
+    eliminate_effect_of_other_invoices
   end
 
   def test_show_balance
@@ -14,15 +14,31 @@ class ListInvoicesTest < ApplicationSystemTestCase
     assert_text "Your current account balance is 100,00 EUR"
   end
 
-  def test_show_multiple_invoices
-    @invoices = invoices
-    @registrar_invoices = []
-    @invoices.each do |invoice|
-      @registrar_invoices << invoice
-    end
+  def test_show_invoices_of_current_registrar
+    registrar = registrars(:bestnames)
+    @user.update!(registrar: registrar)
+    @invoice.update!(seller: registrar)
 
-    visit registrar_invoices_path
-    assert_text "Unpaid", count: 5
-    assert_text "Invoice no.", count: 7
+    visit registrar_invoices_url
+
+    assert_css '.invoice'
   end
-end
+
+  def test_do_not_show_invoices_of_other_registrars
+    registrar = registrars(:goodnames)
+    @user.update!(registrar: registrar)
+    @invoice.update!(seller: registrar)
+
+    visit registrar_invoices_url
+
+    assert_no_css '.invoice'
+  end
+
+  private
+
+  def eliminate_effect_of_other_invoices
+    Invoice.connection.disable_referential_integrity do
+      Invoice.delete_all("id != #{@invoice.id}")
+    end
+  end
+end

test/system/registrar_area/invoices/payment_callback_test.rb

@@ -12,8 +12,8 @@ class PaymentCallbackTest < ApplicationSystemTestCase
     @invoice = invoices(:for_payments_test)
     invoice_item = invoice_items(:one)
 
-    @invoice.invoice_items << invoice_item
-    @invoice.invoice_items << invoice_item
+    @invoice.items << invoice_item
+    @invoice.items << invoice_item
     @user.registrar.invoices << @invoice
   end
 

test/system/registrar_area/invoices/payment_return_test.rb

@@ -12,8 +12,8 @@ class PaymentReturnTest < ApplicationSystemTestCase
     @invoice = invoices(:for_payments_test)
     invoice_item = invoice_items(:one)
 
-    @invoice.invoice_items << invoice_item
-    @invoice.invoice_items << invoice_item
+    @invoice.items << invoice_item
+    @invoice.items << invoice_item
     @user.registrar.invoices << @invoice
   end
 

test/system/registrar_area/invoices_test.rb

@@ -0,0 +1,20 @@
+require 'test_helper'
+
+class RegistrarAreaInvoicesTest < ApplicationSystemTestCase
+  setup do
+    sign_in users(:api_bestnames)
+    @invoice = invoices(:one)
+  end
+
+  def test_cancels_an_invoice
+    @invoice.account_activity = nil
+    assert @invoice.cancellable?
+
+    visit registrar_invoice_url(@invoice)
+    click_on 'Cancel'
+    @invoice.reload
+
+    assert @invoice.cancelled?
+    assert_text 'Invoice has been cancelled'
+  end
+end