Fixed unique constraint issue for subchannel model

Subchannel unique constraint now applies to a matching pair of channel_id and subscription, oppose to the previous constraint; unique subscription only.

apps/home/migrations/0005_alter_subchannel_options_and_more.py

@@ -0,0 +1,27 @@
+# Generated by Django 5.0.1 on 2024-04-28 14:50
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('home', '0004_remove_subchannel_subscription_id_and_more'),
+    ]
+
+    operations = [
+        migrations.AlterModelOptions(
+            name='subchannel',
+            options={'get_latest_by': 'id', 'verbose_name': 'SubChannel', 'verbose_name_plural': 'SubChannels'},
+        ),
+        migrations.AlterField(
+            model_name='subchannel',
+            name='subscription',
+            field=models.ForeignKey(help_text='The linked Subscription, must be unique.', on_delete=django.db.models.deletion.CASCADE, to='home.subscription'),
+        ),
+        migrations.AddConstraint(
+            model_name='subchannel',
+            constraint=models.UniqueConstraint(fields=('channel_id', 'subscription'), name='unique channel id and subscription pair'),
+        ),
+    ]

apps/home/models.py

@@ -125,10 +125,24 @@ class SubChannel(models.Model):
     subscription = models.ForeignKey(
         to="home.Subscription",
         on_delete=models.CASCADE,
-        unique=True,
         help_text=_("The linked Subscription, must be unique.")
     )
 
+    class Meta:
+        """
+        Metadata for the SubChannel Model.
+        """
+
+        verbose_name = "SubChannel"
+        verbose_name_plural = "SubChannels"
+        get_latest_by = "id"
+        constraints = [
+            # Prevent servers from having subscriptions with duplicate names
+            models.UniqueConstraint(
+                fields=["channel_id", "subscription"],
+                name="unique channel id and subscription pair")
+        ]
+
 
 class Subscription(models.Model):
     id = models.AutoField(primary_key=True)