SchoolSchedule weekday unique

apps/school/models.py

@@ -11,7 +11,7 @@ class SchoolSchedule(models.Model):
         (6, 'суббота'),
         (7, 'воскресенье'),
     )
-    weekday = models.PositiveSmallIntegerField('День недели', choices=WEEKDAY_CHOICES)
+    weekday = models.PositiveSmallIntegerField('День недели', choices=WEEKDAY_CHOICES, unique=True)
     title = models.CharField('Заголовок', default='', max_length=100, db_index=True)
     description = models.TextField('Описание')
     materials = models.TextField('Материалы')