feat(zarinhub): automate access token refresh

backend/cmd/api/main.go

@@ -38,6 +38,24 @@ func run(logger *slog.Logger) error {
 		return fmt.Errorf("load configuration: %w", err)
 	}
 
+	httpClient := &http.Client{Timeout: config.ZarinHubTimeout}
+	tokenManager := zarinhub.NewTokenManager(
+		httpClient,
+		config.ZarinHubAuthEndpoint,
+		config.ZarinHubUsername,
+		config.ZarinHubPassword,
+	)
+
+	authContext, cancelAuth := context.WithTimeout(
+		context.Background(),
+		config.ZarinHubTimeout,
+	)
+	_, err = tokenManager.AccessToken(authContext)
+	cancelAuth()
+	if err != nil {
+		return fmt.Errorf("authenticate with zarinhub: %w", err)
+	}
+
 	db, err := storage.OpenSQLite(config.DatabasePath)
 	if err != nil {
 		return err
@@ -58,9 +76,9 @@ func run(logger *slog.Logger) error {
 	}
 
 	zarinHubClient := zarinhub.NewClient(
-		&http.Client{Timeout: config.ZarinHubTimeout},
+		httpClient,
 		config.ZarinHubEndpoint,
-		config.ZarinHubToken,
+		tokenManager,
 	)
 	cardService := service.NewCardService(zarinHubClient)
 	auditRepository := repository.NewAuditRepository(db)