Only allow unique emails for user accounts

app/users/migrations/0002_alter_customuser_email.py

@@ -0,0 +1,21 @@
+# Generated by Django 3.2.15 on 2022-11-08 11:19
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [("users", "0001_initial")]
+
+    operations = [
+        migrations.AlterField(
+            model_name="customuser",
+            name="email",
+            field=models.EmailField(
+                error_messages={"unique": "A user with that email already exists."},
+                max_length=254,
+                unique=True,
+                verbose_name="email address",
+            ),
+        )
+    ]

app/users/models.py

@@ -1,5 +1,13 @@
 from django.contrib.auth.models import AbstractUser
+from django.utils.translation import gettext_lazy as _
+from django.db.models import EmailField
 
 
 class CustomUser(AbstractUser):
-    pass
+    email = EmailField(
+        _("email address"),
+        blank=False,
+        error_messages={"unique": _("A user with that email already exists.")},
+        null=False,
+        unique=True,
+    )