Fix an Internal Server Error while creating K8s CloudServerTemplate

@yas, I have the following comment about this patch.

+++ b/modules/cloud_service_providers/k8s/src/Form/K8sCreateForm.php
@@ -36,11 +40,54 @@ class K8sCreateForm extends K8sContentForm {
+      $cloud_service_providers = $this->entityTypeManager
+        ->getStorage('cloud_config')
+        ->loadByProperties([
+          'type' => 'k8s',
+          'cloud_context' => $cloud_context,
+        ]);
+
+      if (!empty($cloud_service_providers)) {
+
+        $cloud_service_provider = array_shift($cloud_service_providers);
+        $name = $cloud_service_provider->getName();
+
+        $page_link = Link::fromTextAndUrl(
+          $name, Url::fromRoute(
+            'entity.cloud_config.edit_form',
+            ['cloud_config' => $cloud_service_provider->id()]
+          )
+        )->toString();
+
+        \Drupal::messenger()->addError(
+          t('The endpoint is unreachable. Please check the API server and token: @page_link', [
+            '@page_link' => $page_link,
+          ])
+        );
+      }
+
+      $this->messenger->addError($e->getMessage());
+
+      $url = Url::fromRoute("entity.{$this->entity->getEntityTypeId()}.collection", [
+        'cloud_context' => $cloud_context,
+      ]);
+
+      $redirect_response = new RedirectResponse($url->toString());
+      $redirect_response->send();
+      $this->messenger->addError($e->getMessage());

Can some of this be abstracted into a common method in K8sContentForm?

I ask because the same logic appears in K8sNamespaceCreateForm as well.

@yas, thank you for the updated patch. I have two more comments below.

1. +++ b/modules/cloud_service_providers/k8s/src/Service/K8sService.php
   @@ -1725,12 +1731,72 @@ class K8sService implements K8sServiceInterface {
   +    \Drupal::messenger()->addError(
   +      t('The endpoint is unreachable.')
   +    );
   

   Can you use $this->messenger instead of \Drupal::messenger()?

2. +++ b/modules/cloud_service_providers/k8s/src/Service/K8sService.php
   @@ -1725,12 +1731,72 @@ class K8sService implements K8sServiceInterface {
   +      \Drupal::messenger()->addError(
   +        t('Please check the API server and token: @page_link', [
   +          '@page_link' => $page_link,
   +        ])
   +      );
   

   Can you use $this->messenger instead of \Drupal::messenger()

@yas,. Looks good!