[wireguard] add unique constrain for keys in pool

uncloud_net/migrations/0006_auto_20201224_1626.py

@@ -0,0 +1,17 @@
+# Generated by Django 3.1 on 2020-12-24 16:26
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('uncloud_net', '0005_auto_20201220_1837'),
+    ]
+
+    operations = [
+        migrations.AddConstraint(
+            model_name='wireguardvpn',
+            constraint=models.UniqueConstraint(fields=('vpnpool', 'wireguard_public_key'), name='wg_key_unique_per_pool'),
+        ),
+    ]

uncloud_net/models.py

@@ -84,6 +84,13 @@ class WireGuardVPN(models.Model):
 
     wireguard_public_key = models.CharField(max_length=48, unique=True)
 
+    class Meta:
+        constraints = [
+            models.UniqueConstraint(fields=['vpnpool', 'wireguard_public_key'],
+                                    name='wg_key_unique_per_pool')
+        ]
+
+
     @property
     def network_mask(self):
         return self.vpnpool.subnetwork_mask