feat: send email to user when api key expires within 7 days (#451)

Co-authored-by: Elias Schneider <login@eliasschneider.com>

backend/internal/job/api_key_expiry_job.go

@@ -0,0 +1,49 @@
+package job
+
+import (
+	"context"
+	"log"
+
+	"github.com/go-co-op/gocron/v2"
+	"github.com/pocket-id/pocket-id/backend/internal/service"
+)
+
+type ApiKeyEmailJobs struct {
+	apiKeyService    *service.ApiKeyService
+	appConfigService *service.AppConfigService
+}
+
+func RegisterApiKeyExpiryJob(ctx context.Context, apiKeyService *service.ApiKeyService, appConfigService *service.AppConfigService) {
+	jobs := &ApiKeyEmailJobs{
+		apiKeyService:    apiKeyService,
+		appConfigService: appConfigService,
+	}
+
+	scheduler, err := gocron.NewScheduler()
+	if err != nil {
+		log.Fatalf("Failed to create a new scheduler: %v", err)
+	}
+
+	registerJob(ctx, scheduler, "ExpiredApiKeyEmailJob", "0 0 * * *", jobs.checkAndNotifyExpiringApiKeys)
+
+	scheduler.Start()
+}
+
+func (j *ApiKeyEmailJobs) checkAndNotifyExpiringApiKeys(ctx context.Context) error {
+
+	apiKeys, err := j.apiKeyService.ListExpiringApiKeys(ctx, 7)
+	if err != nil {
+		log.Printf("Failed to list expiring API keys: %v", err)
+		return err
+	}
+
+	for _, key := range apiKeys {
+		if key.User.Email == "" {
+			continue
+		}
+		if err := j.apiKeyService.SendApiKeyExpiringSoonEmail(ctx, key); err != nil {
+			log.Printf("Failed to send email for key %s: %v", key.ID, err)
+		}
+	}
+	return nil
+}