Added email alerter class

src/EmailAlerter.php

@@ -0,0 +1,38 @@
+<?php declare(strict_types = 1);
+
+namespace Drupal\opencase;
+use Drupal\user\Entity\User;
+
+class EmailAlerter {
+    public function send_email_to_users_with_role(array $params, string $key, string $role): void {
+        $mailManager = \Drupal::service('plugin.manager.mail');
+        $module = 'goodnightout_opencase';
+        $to = implode(',', $this->get_email_addresses_of_users_with_role($role));
+        $send = true;
+        $result = $mailManager->mail($module, $key, $to, NULL, $params, NULL, $send);
+        if ($result['result'] != true) {
+            $message = t('There was a problem sending your email notification to @email.', array('@email' => $to));
+            \Drupal::messenger()->addMessage($message, 'error');
+            \Drupal::logger('mail-log')->error($message);
+            return;
+        }
+        $message = t('An email notification has been sent to @email ', array('@email' => $to));
+        \Drupal::messenger()->addMessage($message);
+        \Drupal::logger('mail-log')->notice($message);
+    }
+    
+    private function get_email_addresses_of_users_with_role(string $role): array {
+        $email_addresses = [];
+        $ids = \Drupal::entityQuery('user')
+            ->condition('status', 1)
+            ->condition('roles', $role)
+            ->execute();
+            $users = User::loadMultiple($ids);
+            foreach($users as $user){
+                $email_addresses[] = $user->getEmail();
+            } 
+        return $email_addresses;
+    }
+}
+
+