feat(users): normalize email identity storage

apps/users/migrations/0003_normalize_user_email_identity.py

@@ -0,0 +1,63 @@
+# Generated by Django 5.2.12 on 2026-05-14
+
+from django.db import migrations, models
+from django.db.models import Q
+from django.db.models.functions import Lower
+
+
+def _normalize_email(value):
+    if value is None:
+        return None
+    normalized = value.strip().lower()
+    return normalized or None
+
+
+def normalize_user_and_social_emails(apps, schema_editor):
+    User = apps.get_model("users", "User")
+    UserSocialAccount = apps.get_model("users", "UserSocialAccount")
+
+    seen_emails = set()
+    for user in User.objects.all().order_by("created_at", "id"):
+        normalized_email = _normalize_email(user.email)
+        if normalized_email in seen_emails:
+            normalized_email = None
+        elif normalized_email is not None:
+            seen_emails.add(normalized_email)
+
+        if user.email != normalized_email:
+            user.email = normalized_email
+            user.save(update_fields=["email"])
+
+    for social_account in UserSocialAccount.objects.all().order_by("created_at", "id"):
+        normalized_email = _normalize_email(social_account.email)
+        if social_account.email != normalized_email:
+            social_account.email = normalized_email
+            social_account.save(update_fields=["email"])
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("users", "0002_usersocialaccount"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="user",
+            name="email",
+            field=models.EmailField(blank=True, default=None, max_length=254, null=True),
+        ),
+        migrations.AlterField(
+            model_name="usersocialaccount",
+            name="email",
+            field=models.EmailField(blank=True, default=None, max_length=254, null=True),
+        ),
+        migrations.RunPython(normalize_user_and_social_emails, migrations.RunPython.noop),
+        migrations.AddConstraint(
+            model_name="user",
+            constraint=models.UniqueConstraint(
+                Lower("email"),
+                condition=Q(email__isnull=False),
+                name="user_email_ci_uniq",
+            ),
+        ),
+    ]