Allow none values for release_date fields

courses/migrations/0037_auto_20211129_1752.py

+# Generated by Django 2.2.24 on 2021-11-29 20:52
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('courses', '0036_auto_20211125_1203'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='lesson',
+            name='release_date',
+            field=models.DateTimeField(blank=True, default=None, null=True, verbose_name='Date'),
+        ),
+        migrations.AlterField(
+            model_name='unit',
+            name='release_date',
+            field=models.DateTimeField(blank=True, default=None, null=True, verbose_name='Date'),
+        ),
+    ]

courses/models.py

@@ -922,7 +922,9 @@ class Lesson(PositionedModel):
     )
     release_date = models.DateTimeField(
         _('Date'),
-        default=timezone.now
+        null=True,
+        blank=True,
+        default=None,
     )
 
     collection_name = 'course'
@@ -1019,7 +1021,9 @@ class Unit(PositionedModel):
     )
     release_date = models.DateTimeField(
         _('Date'),
-        default=timezone.now
+        null=True,
+        blank=True,
+        default=None,
     )
 
     collection_name = 'lesson'