BIG UPD: migrate to python 3.10 and django 3.2

dav_events/models/participant.py

@@ -4,7 +4,6 @@ import datetime
 from django.core.exceptions import ValidationError
 from django.db import models
 from django.utils import timezone
-from django.utils.encoding import python_2_unicode_compatible
 from django.utils.translation import ugettext_lazy as _
 
 from dav_base.validators import DAVNumberValidator
@@ -12,7 +11,6 @@ from dav_base.validators import DAVNumberValidator
 midnight = datetime.time(00, 00, 00)
 
 
-@python_2_unicode_compatible
 class AbstractParticipant(models.Model):
     personal_names = models.CharField(max_length=1024,
                                       verbose_name=_('Vorname(n)'))
@@ -158,9 +156,8 @@ class AbstractParticipant(models.Model):
         return timezone.make_aware(datetime.datetime.combine(purge_date, midnight))
 
 
-@python_2_unicode_compatible
 class Participant(AbstractParticipant):
-    event = models.ForeignKey('Event', related_name='participants')
+    event = models.ForeignKey('Event', related_name='participants', on_delete=models.PROTECT)
     created_at = models.DateTimeField(auto_now_add=True)
     position = models.IntegerField(verbose_name='Listennummer')