Make fields not required. Necessary for lesson cancellation. Closes #30.

biscuit/apps/chronos/migrations/0001_initial.py

@@ -87,10 +87,10 @@ class Migration(migrations.Migration):
                 ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
                 ('week', models.IntegerField(default=biscuit.apps.chronos.util.current_week, verbose_name='Week')),
                 ('lesson_period', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='substitutions', to='chronos.LessonPeriod')),
-                ('room', models.ForeignKey(null=True, on_delete=django.db.models.deletion.CASCADE, to='chronos.Room')),
+                ('room', models.ForeignKey(null=True, blank=True, on_delete=django.db.models.deletion.CASCADE, to='chronos.Room')),
                 ('school', models.ForeignKey(default=biscuit.core.util.core_helpers.get_current_school, on_delete=django.db.models.deletion.CASCADE, to='core.School')),
-                ('subject', models.ForeignKey(null=True, on_delete=django.db.models.deletion.CASCADE, related_name='lesson_substitutions', to='chronos.Subject')),
-                ('teachers', models.ManyToManyField(related_name='lesson_substitutions', to='core.Person')),
+                ('subject', models.ForeignKey(null=True, blank=True, on_delete=django.db.models.deletion.CASCADE, related_name='lesson_substitutions', to='chronos.Subject')),
+                ('teachers', models.ManyToManyField(null=True, blank=True, related_name='lesson_substitutions', to='core.Person')),
             ],
             options={
                 'ordering': ['lesson_period__lesson__date_start', 'week', 'lesson_period__period__weekday', 'lesson_period__period__period'],