feat: add fallback default pool validation

program/migrations/0103_alter_radiosettings_fallback_default_pool.py

+# Generated by Django 4.2.13 on 2024-06-25 20:00
+
+import program.models
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("program", "0102_radiosettings_fallback_pools"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="radiosettings",
+            name="fallback_default_pool",
+            field=models.CharField(
+                blank=True,
+                max_length=32,
+                validators=[program.models.validate_fallback_default_pool],
+            ),
+        ),
+    ]

program/models.py

@@ -617,6 +617,11 @@ def validate_fallback_pools(value):
     validate_value(value, schema)
 
 
+def validate_fallback_default_pool(value):
+    if value not in RadioSettings.objects.first().fallback_pools.values():
+        raise DjangoValidationError(f"Pool '{value}' does not exist in fallback pools.")
+
+
 class RadioSettings(models.Model):
     cba_api_key = models.CharField(blank=True, max_length=64, verbose_name="CBA API key")
     cba_domains = models.JSONField(
@@ -626,7 +631,9 @@ class RadioSettings(models.Model):
         validators=[validate_cba_domains],
         verbose_name="CBA domains",
     )
-    fallback_default_pool = models.CharField(blank=True, max_length=32)
+    fallback_default_pool = models.CharField(
+        blank=True, max_length=32, validators=[validate_fallback_default_pool]
+    )
     fallback_pools = models.JSONField(
         blank=True,
         default=dict,