fix: rule assignements lost of channel update

Fix bug where updating notification channel resulted in notification
rules get unassigned on Svix side due to no rule assignement information
passed in update API call.

openmeter/notification/service/channel.go

@@ -178,6 +178,22 @@ func (s Service) UpdateChannel(ctx context.Context, params notification.UpdateCh
 	}
 
 	txFunc := func(ctx context.Context, repo notification.TxRepository) (*notification.Channel, error) {
+		// Fetch rules assigned to channel as we need to make sure that we do not remove rule assignments
+		// from channel during update.
+		rules, err := s.repo.ListRules(ctx, notification.ListRulesInput{
+			Namespaces:      []string{params.Namespace},
+			IncludeDisabled: true,
+			Channels:        []string{params.ID},
+		})
+		if err != nil {
+			return nil, fmt.Errorf("failed to list rules for channel: %w", err)
+		}
+
+		ruleIDs := make([]string, 0, len(rules.Items))
+		for _, rule := range rules.Items {
+			ruleIDs = append(ruleIDs, rule.ID)
+		}
+
 		channel, err = repo.UpdateChannel(ctx, params)
 		if err != nil {
 			return nil, fmt.Errorf("failed to create channel: %w", err)
@@ -204,6 +220,7 @@ func (s Service) UpdateChannel(ctx context.Context, params notification.UpdateCh
 					ChannelIDMetadataKey: channel.ID,
 				},
 				Description: convert.ToPointer("Notification Channel: " + channel.ID),
+				Channels:    ruleIDs,
 			})
 			if err != nil {
 				return nil, fmt.Errorf("failed to update webhook for channel: %w", err)