Propagate error details to REST API responses

[MAILPOET-4659]

mailpoet/lib/API/REST/ErrorResponse.php

@@ -6,13 +6,17 @@ class ErrorResponse extends Response {
   public function __construct(
     int $status,
     string $message,
-    string $code
+    string $code,
+    array $errors = []
   ) {
     parent::__construct(null, $status);
     $this->set_data([
       'code' => $code,
       'message' => $message,
-      'data' => ['status' => $status],
+      'data' => [
+        'status' => $status,
+        'errors' => $errors,
+      ],
     ]);
   }
 }