Add migration that links individual members to users by email

Co-authored-by: Sarah Boyce <[email protected]>

Author: ertgl

members/migrations/0012_auto_20251021_2353.py

@@ -0,0 +1,46 @@
+# Generated by Django 5.2.7 on 2025-10-21 23:53
+
+from django.conf import settings
+from django.db import migrations, transaction
+
+
+def link_individual_members_to_users_by_email(apps, schema_editor):
+    # These models aren't the ones imported from the `models.py` files.
+    # They're fake, and constructed based on the historical migrations.
+    # Ensure that the `Migration.dependencies` contains the migrations needed to
+    # construct the models that are used here.
+    IndividualMember = apps.get_model("members.IndividualMember")
+    User = apps.get_model(settings.AUTH_USER_MODEL)
+
+    individual_members_queryset = IndividualMember.objects.filter(
+        user_id__isnull=True,
+    ).select_for_update(
+        nowait=False,
+    )
+    users_queryset = User.objects.filter(
+        email__in=individual_members_queryset.values_list("email", flat=True),
+    )
+    for user in users_queryset.iterator():
+        with transaction.atomic():
+            IndividualMember.objects.filter(email=user.email).update(user=user)
+
+
+def noop(apps, schema_editor):
+    pass
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("auth", "0012_alter_user_first_name_max_length"),
+        ("members", "0011_alter_individualmember_options_and_more"),
+    ]
+
+    operations = [
+        migrations.RunPython(
+            link_individual_members_to_users_by_email,
+            # Don't raise `django.db.migrations.exceptions.IrreversibleError`
+            # when reverting to an older migration.
+            reverse_code=noop,
+        ),
+    ]