Drupal 9 Compatibility

Hi, thanks for the patch. I tested it on D8 and D9 with upgrade status which resulted in no errors, so did drupal check on D8. But I have some other php errors and that's why I will leave this as needs review for someone else to look.

-      - '@user.private_tempstore'
+      - '@tempstore.shared'

After this change the module dies:

TypeError: Argument 5 passed to Drupal\simple_recaptcha\SimpleReCaptchaFormManager::__construct() must be an instance of Drupal\Core\TempStore\PrivateTempStoreFactory, instance of Drupal\Core\TempStore\SharedTempStoreFactory given, called in /var/www/html/docroot/core/lib/Drupal/Component/DependencyInjection/Container.php on line 257 in Drupal\simple_recaptcha\SimpleReCaptchaFormManager->__construct() (line 70 of /var/www/html/docroot/modules/contrib/simple_recaptcha/src/SimpleReCaptchaFormManager.php)
#0 /var/www/html/docroot/core/lib/Drupal/Component/DependencyInjection/Container.php(257): Drupal\simple_recaptcha\SimpleReCaptchaFormManager->__construct(Object(Drupal\Core\Config\ConfigFactory), Object(GuzzleHttp\Client), Object(Drupal\Core\Logger\LoggerChannelFactory), Object(Drupal\Core\Extension\ModuleHandler), Object(Drupal\Core\TempStore\SharedTempStoreFactory))
#1 /var/www/html/docroot/core/lib/Drupal/Component/DependencyInjection/Container.php(171): Drupal\Component\DependencyInjection\Container->createService(Array, 'simple_recaptch...')
#2 /var/www/html/docroot/modules/contrib/simple_recaptcha/modules/simple_recaptcha_webform/src/Plugin/WebformHandler/SimpleRecaptchaWebformHandler.php(126): Drupal\Component\DependencyInjection\Container->get('simple_recaptch...')
#3 /var/www/html/docroot/core/lib/Drupal/Core/Plugin/Factory/ContainerFactory.php(21): Drupal\simple_recaptcha_webform\Plugin\WebformHandler\SimpleRecaptchaWebformHandler::create(Object(Drupal\Core\DependencyInjection\Container), Array, 'simple_recaptch...', Array)
#4 /var/www/html/docroot/core/lib/Drupal/Component/Plugin/PluginManagerBase.php(76): Drupal\Core\Plugin\Factory\ContainerFactory->createInstance('simple_recaptch...', Array)
#5 /var/www/html/docroot/modules/contrib/webform/src/Controller/WebformPluginHandlerController.php(135): Drupal\Component\Plugin\PluginManagerBase->createInstance('simple_recaptch...')
#6 [internal function]: Drupal\webform\Controller\WebformPluginHandlerController->listHandlers(Object(Symfony\Component\HttpFoundation\Request), Object(Drupal\webform\Entity\Webform))
#7 /var/www/html/docroot/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(123): call_user_func_array(Array, Array)
#8 /var/www/html/docroot/core/lib/Drupal/Core/Render/Renderer.php(573): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#9 /var/www/html/docroot/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(124): Drupal\Core\Render\Renderer->executeInRenderContext(Object(Drupal\Core\Render\RenderContext), Object(Closure))
#10 /var/www/html/docroot/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(97): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array)
#11 /var/www/html/vendor/symfony/http-kernel/HttpKernel.php(158): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#12 /var/www/html/vendor/symfony/http-kernel/HttpKernel.php(80): Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object(Symfony\Component\HttpFoundation\Request), 1)
#13 /var/www/html/docroot/core/lib/Drupal/Core/StackMiddleware/Session.php(57): Symfony\Component\HttpKernel\HttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#14 /var/www/html/docroot/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(47): Drupal\Core\StackMiddleware\Session->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#15 /var/www/html/docroot/core/modules/page_cache/src/StackMiddleware/PageCache.php(106): Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#16 /var/www/html/docroot/core/modules/page_cache/src/StackMiddleware/PageCache.php(85): Drupal\page_cache\StackMiddleware\PageCache->pass(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#17 /var/www/html/docroot/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(47): Drupal\page_cache\StackMiddleware\PageCache->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#18 /var/www/html/docroot/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(52): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#19 /var/www/html/vendor/stack/builder/src/Stack/StackedHttpKernel.php(23): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#20 /var/www/html/docroot/core/lib/Drupal/Core/DrupalKernel.php(705): Stack\StackedHttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#21 /var/www/html/docroot/index.php(19): Drupal\Core\DrupalKernel->handle(Object(Symfony\Component\HttpFoundation\Request))
#22 {main}

Step 1: switch from deprecated user.private_tempstore service to tempstore.private

Step 2: reformat DI in SimpleRecaptchaWebformHandler to fix compatibility with webform 6.x branch

#9 works fine. Thanks

Reroll after implementing initial tests in #3152625, it required same changes in info file and deprecation fixes in services.yml file

Committed to dev, new release will follow tonight,
patch is already passing first pack of tests, I will be working on more test coverage in coming days through #3152625
Thanks to all of you for help and reviews!