fix(m3u): enhance custom properties handling and DB connection management

- Implemented `ensure_custom_properties_dict()` to normalize custom properties across various models and serializers, addressing issues with legacy JSON-encoded strings.
- Updated M3U account and channel group models to ensure custom properties are consistently stored as dictionaries during save operations.
- Enhanced Celery task management by ensuring old DB connections are closed before and after tasks, improving reliability and preventing errors during account refresh operations. (Fixes #1338)

tests/test_custom_properties_as_dict.py

@@ -0,0 +1,74 @@
+import uuid
+
+from django.test import SimpleTestCase, TestCase
+
+from core.utils import custom_properties_as_dict, ensure_custom_properties_dict
+from apps.m3u.models import M3UAccount, M3UAccountProfile
+from apps.channels.models import ChannelGroupM3UAccount, ChannelGroup
+
+
+class CustomPropertiesAsDictTests(SimpleTestCase):
+    def test_dict_passthrough(self):
+        value = {"enable_vod": True}
+        self.assertIs(custom_properties_as_dict(value), value)
+
+    def test_json_string_parsed(self):
+        self.assertEqual(
+            custom_properties_as_dict('{"enable_vod": true}'),
+            {"enable_vod": True},
+        )
+
+    def test_non_json_string_returns_empty_dict(self):
+        self.assertEqual(custom_properties_as_dict("not-json"), {})
+
+    def test_json_array_returns_empty_dict(self):
+        self.assertEqual(custom_properties_as_dict("[1, 2]"), {})
+
+    def test_none_returns_empty_dict(self):
+        self.assertEqual(custom_properties_as_dict(None), {})
+
+
+class EnsureCustomPropertiesDictTests(SimpleTestCase):
+    def test_dict_passthrough_without_reparse(self):
+        value = {"enable_vod": True}
+        self.assertIs(ensure_custom_properties_dict(value), value)
+
+    def test_none_returns_empty_dict(self):
+        self.assertEqual(ensure_custom_properties_dict(None), {})
+
+
+class CustomPropertiesSaveNormalizationTests(TestCase):
+    def test_m3u_account_save_rewrites_string_custom_properties(self):
+        account = M3UAccount.objects.create(
+            name=f"Test Account {uuid.uuid4().hex[:8]}",
+            custom_properties='{"enable_vod": true}',
+        )
+        account.refresh_from_db()
+        self.assertEqual(account.custom_properties, {"enable_vod": True})
+
+    def test_profile_save_rewrites_string_custom_properties(self):
+        account = M3UAccount.objects.create(
+            name=f"Test Account {uuid.uuid4().hex[:8]}"
+        )
+        profile = M3UAccountProfile.objects.get(
+            m3u_account=account, is_default=True
+        )
+        profile.custom_properties = '{"notes": "hello"}'
+        profile.save(update_fields=["custom_properties"])
+        profile.refresh_from_db()
+        self.assertEqual(profile.custom_properties, {"notes": "hello"})
+
+    def test_group_relation_save_rewrites_string_custom_properties(self):
+        account = M3UAccount.objects.create(
+            name=f"Test Account {uuid.uuid4().hex[:8]}"
+        )
+        group = ChannelGroup.objects.create(
+            name=f"Sports {uuid.uuid4().hex[:8]}"
+        )
+        rel = ChannelGroupM3UAccount.objects.create(
+            m3u_account=account,
+            channel_group=group,
+            custom_properties='{"force_dummy_epg": true}',
+        )
+        rel.refresh_from_db()
+        self.assertEqual(rel.custom_properties, {"force_dummy_epg": True})