feat: make email optional for under-16 participants except applicant

src/Form/Model/ParticipantDto.php

@@ -80,11 +80,17 @@ class ParticipantDto
     #[Assert\NotNull(message: 'Bitte angeben', groups: ['strict_required'])]
     public ?\DateTimeImmutable $dateOfBirth = null;
 
-    // Every participant needs an email address: BusPro rejects the step-3 Anfrage with 650
-    // otherwise, children included. Under-16s have the applicant's address pre-filled by
-    // ParticipantEmailFieldHandler and may override it, but may not leave it blank.
+    // BusPro accepts a participant without an email address, so this is the only gate. Under-16s
+    // may leave it blank, everyone else needs one. An under-16 applicant needs one as well; that
+    // case depends on the booking and is enforced by BookingDto::validateFirstParticipantApplicant()
+    // and ParticipantEditDto::validateApplicant(). It stays a property constraint so the missing-field
+    // labels keep their order (see BookingEditPreFlightChecker).
     #[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: 'not this.isChild()',
+        constraints: [new Assert\NotBlank(message: 'Bitte angeben')],
+        groups: ['strict_required'],
+    )]
     public ?string $email = null;
 
     public ?string $mobile = null;
@@ -530,6 +536,28 @@ class ParticipantDto
         }
     }
 
+    /**
+     * Validates that this person, as the booking's contact, has an email address.
+     *
+     * The property constraint on $email already holds everyone aged 16 or older (and anyone
+     * without a date of birth) to it, so this only adds the under-16 contact and never reports
+     * the same field twice. Like validateAddressFields(), the callers decide who the contact is.
+     */
+    public function validateApplicantEmail(ExecutionContextInterface $context, string $pathPrefix = ''): void
+    {
+        if (false === $this->isChild()) {
+            return;
+        }
+
+        if (null !== $this->email && false === u($this->email)->trim()->isEmpty()) {
+            return;
+        }
+
+        $context->buildViolation('Bitte angeben')
+            ->atPath($pathPrefix.'email')
+            ->addViolation();
+    }
+
     /**
      * Validates that this person has a complete address.
      *