added functionality to Serializer validate method

Sistemas/migrations/0003_device_token_device_username.py

@@ -0,0 +1,26 @@
+# Generated by Django 4.1.3 on 2023-01-23 17:18
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('authtoken', '0003_tokenproxy'),
+        ('Sistemas', '0002_device_alter_sistemas_por_cliente_options_and_more'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='device',
+            name='token',
+            field=models.OneToOneField(blank=True, null=True, on_delete=django.db.models.deletion.CASCADE, to='authtoken.token'),
+        ),
+        migrations.AddField(
+            model_name='device',
+            name='username',
+            field=models.CharField(default=1, max_length=150, unique=True),
+            preserve_default=False,
+        ),
+    ]