wip: booking process, refactoring

src/BusProNet/Model/Communication.php

@@ -15,14 +15,14 @@ use Symfony\Component\Validator\Constraints as Assert;
  */
 class Communication
 {
-    public string $phone = '';
+    public ?string $phone = null;
 
     #[Assert\NotBlank(message: 'Bitte angeben', groups: ['personal_data'])]
-    public string $mobile = '';
+    public ?string $mobile = null;
 
     #[Assert\NotBlank(message: 'Bitte angeben', groups: ['personal_data'])]
     #[Assert\Email(message: 'Bitte eine gültige Adresse angeben', mode: 'strict', groups: ['personal_data'])]
-    public string $email = '';
+    public ?string $email = null;
 
     public bool $newsletter = false;