Change inheritance structure to match the one from Rails 5 more

In the future, ApplicationSystemTestCase should inherit from
ActionDispatch::SystemTestCase and JavaScriptApplicationSystemTestCase
could possibly be removed if the `driven_by` method works as it is
promised in Rails documentation:

http://api.rubyonrails.org/v5.2/classes/ActionDispatch/SystemTestCase.html

Consider introducing another class between
ActionDispatch::IntegrationTest and other items inheriting from it, as
the general Rails practice seems to have `ApplicationIntegrationTest`,
as we do have `ApplicationRecord` and `ApplicationController`.

test/application_system_test_case.rb

@@ -0,0 +1,42 @@
+require 'test_helper'
+
+require 'database_cleaner'
+require 'selenium/webdriver'
+
+class ApplicationSystemTestCase < ActionDispatch::IntegrationTest; end
+
+class JavaScriptApplicationSystemTestCase < ApplicationSystemTestCase
+  self.use_transactional_fixtures = false
+  DatabaseCleaner.strategy = :truncation
+
+  Capybara.register_driver(:chrome) do |_app|
+    options = ::Selenium::WebDriver::Chrome::Options.new
+
+    options.add_argument('--headless')
+    options.add_argument('--no-sandbox')
+    options.add_argument('--disable-dev-shm-usage')
+    options.add_argument('--window-size=1400,1400')
+
+    Capybara::Selenium::Driver.new(Rails.application, browser: :chrome, options: options)
+  end
+
+  Capybara.register_server(:silent_puma) do |app, port, _host|
+    require 'rack/handler/puma'
+    Rack::Handler::Puma.run(app, Port: port, Threads: '0:2', Silent: true)
+  end
+
+  def setup
+    DatabaseCleaner.start
+
+    super
+
+    Capybara.current_driver = :chrome
+    Capybara.server = :silent_puma
+  end
+
+  def teardown
+    super
+
+    DatabaseCleaner.clean
+  end
+end