Move WP translation function from __construct

According to this post https://make.wordpress.org/core/2024/10/21/i18n-improvements-6-7/, we are currently doing_it_wrong

MAILPOET-6298

mailpoet/lib/API/JSON/ErrorHandler.php

@@ -7,15 +7,11 @@ use MailPoet\HttpAwareException;
 
 class ErrorHandler {
   /** @var string[] */
-  private $defaultErrors;
+  private $defaultErrors = [];
-
-  public function __construct() {
-    $this->defaultErrors = [
-      Error::UNKNOWN => __('An unknown error occurred.', 'mailpoet'),
-    ];
-  }
 
   public function convertToResponse(\Throwable $e): ErrorResponse {
+    $this->defaultErrors[Error::UNKNOWN] = __('An unknown error occurred.', 'mailpoet');
+
     if ($e instanceof Exception) {
       $errors = $e->getErrors() ?: $this->defaultErrors;
       $statusCode = $e instanceof HttpAwareException ? $e->getHttpStatusCode() : Response::STATUS_UNKNOWN;

mailpoet/lib/Automation/Engine/Registry.php

@@ -56,6 +56,13 @@ class Registry {
     $this->wordPress = $wordPress;
     $this->steps[$rootStep->getKey()] = $rootStep;
 
+    $this->wordPress->addAction('init', [
+      $this,
+      'setupTemplateCategories',
+    ]);
+  }
+
+  public function setupTemplateCategories () {
     $this->templateCategories = [
       'welcome' => new AutomationTemplateCategory('welcome', __('Welcome', 'mailpoet')),
       'abandoned-cart' => new AutomationTemplateCategory('abandoned-cart', __('Abandoned Cart', 'mailpoet')),

mailpoet/lib/WooCommerce/TransactionalEmails.php

@@ -42,6 +42,13 @@ class TransactionalEmails {
     $this->template = $template;
     $this->woocommerceHelper = $woocommerceHelper;
     $this->newslettersRepository = $newslettersRepository;
+    $this->wp->addAction('init', [
+      $this,
+      'setupEmailHeadings',
+    ]);
+  }
+
+  public function setupEmailHeadings() {
     $this->emailHeadings = [
       'new_account' => [
         'option_name' => 'woocommerce_new_order_settings',