feat: functionality to determine family status of a booking

src/Form/Model/ParticipantDto.php

@@ -106,4 +106,23 @@ class ParticipantDto
     {
         return 'O' === $this->status;
     }
+
+    /**
+     * Calculates the participant's current age in complete years.
+     *
+     * Uses the same logic as existing age evaluators in the system
+     * for consistency across age-related calculations.
+     *
+     * @return int|null The calculated age in complete years, or null if no birth date
+     */
+    public function getAge(): ?int
+    {
+        if (null === $this->dateOfBirth) {
+            return null;
+        }
+
+        $today = new \DateTimeImmutable();
+
+        return $this->dateOfBirth->diff($today)->y;
+    }
 }