Resolve "get_or_create for lesson documentations and personal notes doesn't work correctly because of missing unique index"

Closes #151 (closed)

aleksis/apps/alsijil/migrations/0012_unique_relation.py

+# Generated by Django 3.1.7 on 2021-03-21 17:04
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('chronos', '0004_substitution_extra_lesson_year'),
+        ('alsijil', '0011_tardiness_positive'),
+    ]
+
+    operations = [
+        migrations.AlterUniqueTogether(
+            name='lessondocumentation',
+            unique_together={('lesson_period', 'week', 'year', 'event', 'extra_lesson')},
+        ),
+        migrations.AlterUniqueTogether(
+            name='personalnote',
+            unique_together={('lesson_period', 'week', 'year', 'event', 'extra_lesson')},
+        ),
+    ]