feat: unique email addresses of participants unless child, cleanup

addresses #869axbn21

src/Form/Service/Abstract/AbstractParticipantFieldHandler.php

@@ -57,7 +57,7 @@ abstract class AbstractParticipantFieldHandler implements ParticipantFieldHandle
      * participant doesn't exist, preventing array access errors.
      *
      * @param BookingDto $bookingDto       The booking DTO containing participants (create or edit)
-     * @param int                 $participantIndex The index of the participant to retrieve
+     * @param int        $participantIndex The index of the participant to retrieve
      *
      * @return object|null The participant object, or null if not found
      */
@@ -82,7 +82,7 @@ abstract class AbstractParticipantFieldHandler implements ParticipantFieldHandle
      */
     protected function isEditMode(BookingDto $bookingDto): bool
     {
-        return $bookingDto->mode === BookingDto::MODE_EDIT;
+        return BookingDto::MODE_EDIT === $bookingDto->mode;
     }
 
     /**
@@ -94,7 +94,7 @@ abstract class AbstractParticipantFieldHandler implements ParticipantFieldHandle
      */
     protected function isCreateMode(BookingDto $bookingDto): bool
     {
-        return $bookingDto->mode === BookingDto::MODE_CREATE;
+        return BookingDto::MODE_CREATE === $bookingDto->mode;
     }
 
     /**
@@ -159,7 +159,7 @@ abstract class AbstractParticipantFieldHandler implements ParticipantFieldHandle
      * processing results.
      *
      * @param array<string, mixed> $submittedData    The submitted participant form data
-     * @param BookingDto  $bookingDto       The booking DTO (potentially modified by processing)
+     * @param BookingDto           $bookingDto       The booking DTO (potentially modified by processing)
      * @param int                  $participantIndex The participant index being processed
      *
      * @return array<string, array<string, mixed>> Empty array (no state modifications by default)