Add telegram details field (#2255)

# What this PR does

## Which issue(s) this PR fixes

## Checklist

- [ ] Unit, integration, and e2e (if applicable) tests updated
- [ ] Documentation added (or `pr:no public docs` PR label added if not
required)
- [ ] `CHANGELOG.md` updated (or `pr:no changelog` PR label added if not
required)

engine/apps/api/serializers/channel_filter.py

@@ -22,9 +22,11 @@ class ChannelFilterSerializer(OrderedModelSerializerMixin, EagerLoadingMixin, se
         required=False,
     )
     slack_channel = serializers.SerializerMethodField()
+    # Duplicated telegram channel and telegram_channel_details field for backwards compatibility for old integration page
     telegram_channel = OrganizationFilteredPrimaryKeyRelatedField(
         queryset=TelegramToOrganizationConnector.objects, filter_field="organization", allow_null=True, required=False
     )
+    telegram_channel_details = serializers.SerializerMethodField()
     order = serializers.IntegerField(required=False)
     filtering_term_as_jinja2 = serializers.SerializerMethodField()
     filtering_term = serializers.CharField(required=False, allow_null=True, allow_blank=True)
@@ -48,8 +50,13 @@ class ChannelFilterSerializer(OrderedModelSerializerMixin, EagerLoadingMixin, se
             "notify_in_telegram",
             "notification_backends",
             "filtering_term_as_jinja2",
+            "telegram_channel_details",
+        ]
+        read_only_fields = [
+            "created_at",
+            "is_default",
+            "telegram_channel_details",
         ]
-        read_only_fields = ["created_at", "is_default"]
 
     def validate(self, data):
         filtering_term = data.get("filtering_term")
@@ -77,6 +84,18 @@ class ChannelFilterSerializer(OrderedModelSerializerMixin, EagerLoadingMixin, se
             "id": obj.slack_channel_pk,
         }
 
+    def get_telegram_channel_details(self, obj) -> dict[str, any] | None:
+        if obj.telegram_channel_id is None:
+            return None
+        try:
+            telegram_channel = TelegramToOrganizationConnector.objects.get(pk=obj.telegram_channel_id)
+            return {
+                "display_name": telegram_channel.channel_name,
+                "id": telegram_channel.channel_chat_id,
+            }
+        except TelegramToOrganizationConnector.DoesNotExist:
+            return None
+
     def validate_slack_channel(self, slack_channel_id):
         SlackChannel = apps.get_model("slack", "SlackChannel")