Memberships: make private by default (amend migration)
The migration `amy/workshops/migrations/0237_auto_20210321_1056.py` sets default value to `private`, but migration `amy/workshops/migrations/0228_auto_20210204_0658.py` introduced the value as public first.

The migrations will have to be changed in order to make production data private by default.
diff --git a/amy/workshops/migrations/0228_auto_20210204_0658.py b/amy/workshops/migrations/0228_auto_20210204_0658.py
index 3eeeea9e..bd8f49f6 100644
--- a/amy/workshops/migrations/0228_auto_20210204_0658.py
+++ b/amy/workshops/migrations/0228_auto_20210204_0658.py
@@ -23,7 +23,7 @@ class Migration(migrations.Migration):
         migrations.AddField(
             model_name='membership',
             name='public_status',
-            field=models.CharField(choices=[('public', 'Public'), ('private', 'Private')], default='public', max_length=20,
+            field=models.CharField(choices=[('public', 'Public'), ('private', 'Private')], default='private', max_length=20,
                                    verbose_name="Can this membership be publicized on The carpentries websites?",
                                    help_text="Public memberships may be listed on any of The Carpentries websites."
             ),
diff --git a/amy/workshops/migrations/0237_auto_20210321_1056.py b/amy/workshops/migrations/0237_auto_20210321_1056.py
index 403a5a5f..c747cbd6 100644
--- a/amy/workshops/migrations/0237_auto_20210321_1056.py
+++ b/amy/workshops/migrations/0237_auto_20210321_1056.py
@@ -82,9 +82,17 @@ class Migration(migrations.Migration):
             model_name='membership',
             name='self_organized_workshops_rolled_over',
         ),
-        migrations.AlterField(
-            model_name='membership',
-            name='public_status',
-            field=models.CharField(choices=[('public', 'Public'), ('private', 'Private')], default='private', help_text='Public memberships may be listed on any of The Carpentries websites.', max_length=20, verbose_name='Can this membership be publicized on The carpentries websites?'),
-        ),
+
+        # The following migration is a no-op as a result of
+        # https://github.com/carpentries/amy/pull/1949
+        # Previously 0228 introduced `public_status` field with default value of `public`,
+        # and this migration changed the default value to `private`. This is however
+        # incorrect as the existing memberships need to be migrated with default value
+        # of `private` first, thus 0228 was amended to have default value as `private`,
+        # and this migration became no-op.
+        # migrations.AlterField(
+        #     model_name='membership',
+        #     name='public_status',
+        #     field=models.CharField(choices=[('public', 'Public'), ('private', 'Private')], default='private', help_text='Public memberships may be listed on any of The Carpentries websites.', max_length=20, verbose_name='Can this membership be publicized on The carpentries websites?'),
+        # ),
     ]
['amy/workshops/migrations/0228_auto_20210204_0658.py', 'amy/workshops/migrations/0237_auto_20210321_1056.py']