feat: split booking between participants and applicant

addresses #869f2q1vu

src/Service/ParticipantFormSupport.php

@@ -40,6 +40,37 @@ class ParticipantFormSupport
         return $participant;
     }
 
+    /**
+     * Builds the traveller that stays behind at index 0 when the applicant stops travelling.
+     *
+     * Only the booking-structural fields carry over. Everything service-shaped was derived from
+     * the applicant's age and no longer applies to whoever actually travels in that slot.
+     */
+    public function createBlankTravellerFrom(ParticipantDto $previous): ParticipantDto
+    {
+        $traveller = new ParticipantDto();
+        $traveller->index = 0;
+        $traveller->assignedRoomId = $previous->assignedRoomId;
+
+        return $traveller;
+    }
+
+    /**
+     * Drops a family insurance selection from every participant.
+     *
+     * Used when a booking turns into a split booking, where family insurance is not offered.
+     */
+    public function clearFamilyInsurance(BookingDto $bookingDto): void
+    {
+        foreach ($bookingDto->participants as $participant) {
+            if (true === $participant->insurance?->familyInsurance) {
+                $participant->insurance = null;
+            }
+
+            $participant->bulkInsuranceBooking = false;
+        }
+    }
+
     public function createParticipantEditDto(BookingDto $bookingDto, int $index): ParticipantEditDto
     {
         return new ParticipantEditDto(