Group Entity Support

I get the following error on the settings page with latest version of the module and Drupal 9.5.9

The website encountered an unexpected error. Please try again later.
Error: Call to undefined method Drupal\group\Entity\GroupRole::isInternal() in Drupal\content_moderation_notifications\Form\ContentModerationNotificationsFormBase::Drupal\content_moderation_notifications\Form\{closure}() (line 248 of modules/contrib/content_moderation_notifications/src/Form/ContentModerationNotificationsFormBase.php).

If I remove the check for isInternal() introduced in #41, then the page loads. However, it still has no group roles appearing on the form as a result of the rest of the change in #41 as I have no "member" role. I have editor and other roles, and none called "member", so I think that change is too restrictive and doesn't work for every scenario.

Updated version of the patch with the change from #41 rolled back.

When testing the actual sending of the notifications I got this error:

The website encountered an unexpected error. Please try again later.

Drupal\Core\Entity\EntityStorageException: The "group_content" entity type does not exist. in Drupal\Core\Entity\Sql\SqlContentEntityStorage->save() (line 815 of core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorage.php).
Drupal\Core\Entity\EntityTypeManager->getHandler('group_content', 'storage') (Line: 192)
Drupal\Core\Entity\EntityTypeManager->getStorage('group_content') (Line: 205)
Drupal\content_moderation_notifications\Notification->sendNotification(Object, Array) (Line: 100)
Drupal\content_moderation_notifications\Notification->processEntity(Object) (Line: 36)
content_moderation_notifications_entity_insert(Object)
call_user_func_array(Object, Array) (Line: 426)
Drupal\Core\Extension\ModuleHandler->Drupal\Core\Extension\{closure}(Object, 'content_moderation_notifications') (Line: 405)
Drupal\Core\Extension\ModuleHandler->invokeAllWith('entity_insert', Object) (Line: 433)
Drupal\Core\Extension\ModuleHandler->invokeAll('entity_insert', Array) (Line: 251)
Drupal\Core\Entity\EntityStorageBase->invokeHook('insert', Object) (Line: 903)
Drupal\Core\Entity\ContentEntityStorageBase->invokeHook('insert', Object) (Line: 598)
Drupal\Core\Entity\EntityStorageBase->doPostSave(Object, ) (Line: 784)
Drupal\Core\Entity\ContentEntityStorageBase->doPostSave(Object, ) (Line: 523)
Drupal\Core\Entity\EntityStorageBase->save(Object) (Line: 804)
Drupal\Core\Entity\Sql\SqlContentEntityStorage->save(Object) (Line: 339)
Drupal\Core\Entity\EntityBase->save() (Line: 270)
Drupal\node\NodeForm->save(Array, Object)
call_user_func_array(Array, Array) (Line: 114)
Drupal\Core\Form\FormSubmitter->executeSubmitHandlers(Array, Object) (Line: 52)
Drupal\Core\Form\FormSubmitter->doSubmitForm(Array, Object) (Line: 595)
Drupal\Core\Form\FormBuilder->processForm('node_blog_form', Array, Object) (Line: 323)
Drupal\Core\Form\FormBuilder->buildForm(Object, Object) (Line: 48)
Drupal\Core\Entity\EntityFormBuilder->getForm(Object, 'default', Array) (Line: 391)
Drupal\group\Entity\Controller\GroupRelationshipController->createForm(Object, 'group_node:blog')
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 580)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 124)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 169)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 81)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 58)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 50)
Drupal\ban\BanMiddleware->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 718)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

This because the "group_content" entity has since been renamed to "group_relationship".

Updated patch attached for that one change.

Here's the patch against the 8.x-3.7 version
The PR is opened for review

@naveenvalecha,
after using your latest patch #50 I get an error on editiong and creating new group notifications:
Error: Call to undefined method Drupal\group\Entity\GroupRole::isInternal()
The full message is:

The website encountered an unexpected error. Try again later.

Error: Call to undefined method Drupal\group\Entity\GroupRole::isInternal() in Drupal\content_moderation_notifications\Form\ContentModerationNotificationsFormBase::Drupal\content_moderation_notifications\Form\{closure}() (line 251 of modules/contrib/content_moderation_notifications/src/Form/ContentModerationNotificationsFormBase.php).
array_filter() (Line: 252)
Drupal\content_moderation_notifications\Form\ContentModerationNotificationsFormBase->buildForm()
call_user_func_array() (Line: 536)
Drupal\Core\Form\FormBuilder->retrieveForm() (Line: 284)
Drupal\Core\Form\FormBuilder->buildForm() (Line: 97)
Drupal\autosave_form\Form\AutosaveFormBuilder->buildForm() (Line: 73)
Drupal\Core\Controller\FormController->getContentResult()
call_user_func_array() (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 638)
Drupal\Core\Render\Renderer->executeInRenderContext() (Line: 124)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext() (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 181)
Symfony\Component\HttpKernel\HttpKernel->handleRaw() (Line: 76)
Symfony\Component\HttpKernel\HttpKernel->handle() (Line: 53)
Drupal\Core\StackMiddleware\Session->handle() (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle() (Line: 28)
Drupal\Core\StackMiddleware\ContentLength->handle() (Line: 32)
Drupal\big_pipe\StackMiddleware\ContentLength->handle() (Line: 116)
Drupal\page_cache\StackMiddleware\PageCache->pass() (Line: 90)
Drupal\page_cache\StackMiddleware\PageCache->handle() (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle() (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle() (Line: 36)
Drupal\Core\StackMiddleware\AjaxPageState->handle() (Line: 51)
Drupal\Core\StackMiddleware\StackedHttpKernel->handle() (Line: 741)
Drupal\Core\DrupalKernel->handle() (Line: 19)