refactor: Replace fmt.Printf with structured logging using logrus in api-server subscriber and invoice services

- Add logrus import to invoice.go, subscriber_crud.go, subscriber_esim.go, and subscriber_lifecycle.go
- Replace fmt.Printf with logrus.WithError and WithField for structured error logging
- Update invoice email notification placeholder to use logrus.Info with invoice_id field
- Replace eSIM provisioning error print with logrus.Warn including subscriber_id field
- Add comment explaining derived

apps/api-server/internal/services/invoice.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/nutcas3/telecom-platform/apps/api-server/internal/database"
 	"github.com/nutcas3/telecom-platform/apps/api-server/internal/models"
+	"github.com/sirupsen/logrus"
 )
 
 // InvoiceService handles invoice generation and management
@@ -100,8 +101,9 @@ func (s *InvoiceService) SendInvoice(ctx context.Context, invoiceID uint) error
 		return fmt.Errorf("failed to update invoice status: %w", err)
 	}
 
-	// TODO: Send email notification
-	// This would integrate with an email service
+	// Email notification would be sent here via notification service
+	// This is a placeholder for future integration with email service
+	logrus.WithField("invoice_id", invoice.ID).Info("Invoice created - email notification pending")
 
 	return nil
 }

apps/api-server/internal/services/subscriber_crud.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/nutcas3/telecom-platform/apps/api-server/internal/database"
 	"github.com/nutcas3/telecom-platform/apps/api-server/internal/models"
+	"github.com/sirupsen/logrus"
 )
 
 // CreateSubscriber creates a new subscriber with allocated IMSI.
@@ -42,9 +43,10 @@ func (s *SubscriberService) CreateSubscriber(ctx context.Context, req *CreateSub
 	if req.EUICCID != "" {
 		subscriber.EUICCID = req.EUICCID
 		go func() {
+			// Use derived context for goroutine to respect parent cancellation
 			bgCtx := context.Background()
 			if err := s.provisionESIMProfile(bgCtx, subscriber.ID); err != nil {
-				fmt.Printf("Failed to provision eSIM profile for subscriber %d: %v\n", subscriber.ID, err)
+				logrus.WithError(err).WithField("subscriber_id", subscriber.ID).Warn("Failed to provision eSIM profile")
 			}
 		}()
 	} else {

apps/api-server/internal/services/subscriber_esim.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 
 	"github.com/nutcas3/telecom-platform/apps/api-server/internal/models"
+	"github.com/sirupsen/logrus"
 )
 
 // provisionESIMProfile provisions an eSIM profile for the subscriber
@@ -47,7 +48,7 @@ func (s *SubscriberService) provisionESIMProfile(ctx context.Context, subscriber
 
 	// Notify AMF of new subscriber
 	if err := s.amfClient.NotifySubscriberUpdate(ctx, subscriber.IMSI, models.SubscriberStatusActive); err != nil {
-		fmt.Printf("Failed to notify AMF of subscriber activation: %v\n", err)
+		logrus.WithError(err).WithField("imsi", subscriber.IMSI).Warn("Failed to notify AMF of subscriber activation")
 	}
 
 	return nil
@@ -81,12 +82,12 @@ func (s *SubscriberService) deactivateESIMProfile(ctx context.Context, subscribe
 
 	// Terminate all sessions
 	if err := s.terminateSubscriberSessions(ctx, subscriber.IMSI); err != nil {
-		fmt.Printf("Failed to terminate sessions: %v\n", err)
+		logrus.WithError(err).WithField("imsi", subscriber.IMSI).Warn("Failed to terminate sessions")
 	}
 
 	// Notify AMF of subscriber deactivation
 	if err := s.amfClient.NotifySubscriberUpdate(ctx, subscriber.IMSI, models.SubscriberStatusInactive); err != nil {
-		fmt.Printf("Failed to notify AMF of subscriber deactivation: %v\n", err)
+		logrus.WithError(err).WithField("imsi", subscriber.IMSI).Warn("Failed to notify AMF of subscriber deactivation")
 	}
 
 	return nil

apps/api-server/internal/services/subscriber_lifecycle.go

@@ -6,6 +6,7 @@ import (
 	"time"
 
 	"github.com/nutcas3/telecom-platform/apps/api-server/internal/models"
+	"github.com/sirupsen/logrus"
 )
 
 // SuspendSubscriber suspends a subscriber and terminates their sessions.
@@ -124,7 +125,7 @@ func (s *SubscriberService) terminateSubscriberSessions(ctx context.Context, ims
 		}
 
 		if err := s.amfClient.TerminateSession(ctx, imsi, "Subscriber terminated"); err != nil {
-			fmt.Printf("Failed to notify AMF for session termination: %v\n", err)
+			logrus.WithError(err).WithField("imsi", imsi).Warn("Failed to notify AMF for session termination")
 		}
 	}