added functionality to Serializer validate method

Sistemas/migrations/0004_alter_device_username.py

@@ -0,0 +1,21 @@
+# Generated by Django 4.1.3 on 2023-01-23 17:22
+
+from django.conf import settings
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+        ('Sistemas', '0003_device_token_device_username'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='device',
+            name='username',
+            field=models.OneToOneField(on_delete=django.db.models.deletion.CASCADE, to=settings.AUTH_USER_MODEL),
+        ),
+    ]