fix: don't require email address from participants under 16

src/Form/Model/ParticipantDto.php

@@ -12,11 +12,20 @@ use App\BusProNet\Model\Service;
 use App\Validator\Constraints as AppAssert;
 use Symfony\Component\Validator\Constraints as Assert;
 use Symfony\Component\Validator\Context\ExecutionContextInterface;
+
 use function Symfony\Component\String\u;
 
 #[AppAssert\Participant(groups: ['booking_edit', 'booking_create'])]
 class ParticipantDto
 {
+    /**
+     * Age below which a participant counts as a child.
+     *
+     * Children may share an email address with an adult and are not required to have one of
+     * their own; both rules go through isChild(), so this is the only place the age lives.
+     */
+    public const CHILD_AGE_THRESHOLD = 16;
+
     /**
      * List of dynamic participant fields that can be conditionally hidden/shown.
      */
@@ -70,8 +79,14 @@ class ParticipantDto
     #[Assert\NotNull(message: 'Bitte angeben', groups: ['strict_required'])]
     public ?\DateTimeImmutable $dateOfBirth = null;
 
+    // Requiredness is delegated to requiresOwnEmail() so the constraint and the field state
+    // conditions cannot state the rule differently.
     #[Assert\Email(message: 'Bitte eine gültige E-Mail Adresse angeben', mode: 'strict', groups: ['booking_edit', 'booking_create'])]
-    #[Assert\NotBlank(message: 'Bitte angeben', groups: ['strict_required'])]
+    #[Assert\When(
+        expression: 'this.requiresOwnEmail()',
+        constraints: [new Assert\NotBlank(message: 'Bitte angeben')],
+        groups: ['strict_required']
+    )]
     public ?string $email = null;
 
     public ?string $mobile = null;
@@ -345,11 +360,25 @@ class ParticipantDto
      * A child is defined as someone under the specified age threshold (default: 16 years).
      * This classification is used for email uniqueness validation (children can share emails with adults).
      *
-     * @param int $ageThreshold The age threshold for child classification (default: 16)
-     *
      * @return bool True if participant is under the age threshold, false otherwise or if age unknown
      */
-    public function isChild(int $ageThreshold = 16): bool
+    /**
+     * Decides whether this participant has to supply an email address of their own.
+     *
+     * The applicant is the booking's contact and always has to be reachable. Everyone else only
+     * needs an address once they are old enough to have one, so children are exempt. An unknown
+     * date of birth counts as an adult, following isChild().
+     *
+     * Single source for the rule: the Assert\When on $email enforces it, and the 'required'
+     * field state conditions in CreateFieldStateProvider/EditFieldStateProvider render the
+     * matching mandatory marker.
+     */
+    public function requiresOwnEmail(): bool
+    {
+        return $this->isApplicant() || false === $this->isChild();
+    }
+
+    public function isChild(int $ageThreshold = self::CHILD_AGE_THRESHOLD): bool
     {
         $age = $this->getAge();