feat: unique email addresses of participants unless child, cleanup

addresses #869axbn21

src/Form/Service/ParticipantRemarksRoomFieldHandler.php

@@ -41,7 +41,7 @@ class ParticipantRemarksRoomFieldHandler extends AbstractParticipantFieldHandler
      * the normalization of empty strings to null values.
      *
      * @param array<string, mixed> $submittedData    The submitted participant form data
-     * @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