feat: unique email addresses of participants unless child, cleanup

addresses #869axbn21

src/Form/Service/ParticipantRentalInsuranceFieldHandler.php

@@ -75,8 +75,7 @@ class ParticipantRentalInsuranceFieldHandler extends AbstractParticipantFieldHan
      * is no longer appropriate for the participant's age, it is automatically cleared.
      *
      * @param array<string, mixed> $submittedData    The submitted participant form data
-     * @param string               $mode             The booking mode (BookingDto::MODE_CREATE or MODE_EDIT)
-     * @param BookingDto  $bookingDto       The booking DTO to update (create or edit)
+     * @param BookingDto           $bookingDto       The booking DTO to update (create or edit)
      * @param int                  $participantIndex The index of the participant being processed
      */
     public function processField(array $submittedData, BookingDto $bookingDto, int $participantIndex): void