Issue #3276745: Create function to check if an email address is allowed to send a message

src/Entity/Form/MailGroupMessageForm.php

@@ -16,24 +16,13 @@ class MailGroupMessageForm extends ContentEntityForm {
   public function validateForm(array &$form, FormStateInterface $form_state) {
     parent::validateForm($form, $form_state);
 
-    /** @var \Drupal\mailgroup\Entity\MailGroupMessageInterface $message */
-    $message = $this->getEntity();
-    $group = $message->getGroup();
-    $sender = $message->getSender();
-
-    if (!$group->isActive()) {
-      $message = $this->t('Message to @group not sent. The group is not active.', [
-        '@group' => $group->getName(),
-      ]);
-      $form_state->setError($form, $message);
+    try {
+      /** @var \Drupal\mailgroup\Entity\MailGroupMessageInterface $message */
+      $message = $this->getEntity();
+      $message->getGroup()->isAllowedToSend($message->getSender());
     }
-
-    if (!$group->isMember($sender)) {
-      $message = $this->t('Message to @group rejected. @email is not a member.', [
-        '@group' => $group->getName(),
-        '@email' => $sender,
-      ]);
-      $form_state->setError($form, $message);
+    catch (\Exception $exception) {
+      $form_state->setError($form, $exception->getMessage());
     }
   }