fix: Allow allow_certificate field to be null in preparation for removing it (#27432)

DEPR-140 MICROBA-985

common/djangoapps/student/migrations/0042_allow_certificate_null_20210427_1519.py

@@ -0,0 +1,18 @@
+# Generated by Django 2.2.20 on 2021-04-27 15:19
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('student', '0041_registration_activation_timestamp'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='userprofile',
+            name='allow_certificate',
+            field=models.BooleanField(default=1, null=True),
+        ),
+    ]

common/djangoapps/student/models.py

@@ -614,7 +614,7 @@ class UserProfile(models.Model):
     )
     state = models.CharField(blank=True, null=True, max_length=2, choices=STATE_CHOICES)
     goals = models.TextField(blank=True, null=True)
-    allow_certificate = models.BooleanField(default=1)
+    allow_certificate = models.BooleanField(default=1, null=True)
     bio = models.CharField(blank=True, null=True, max_length=3000, db_index=False)
     profile_image_uploaded_at = models.DateTimeField(null=True, blank=True)
     phone_regex = RegexValidator(regex=r'^\+?1?\d*$', message="Phone number can only contain numbers.")