Integrate Notification Service into Tender Management System

- Added a new notification service to handle various notification types (email, SMS, push, OTP).
- Implemented configuration for the notification service, allowing customization via environment variables.
- Updated user and customer services to utilize the notification service for sending welcome emails and status updates.
- Introduced a builder pattern for constructing notification requests, enhancing usability and flexibility.
- Enhanced error handling and logging for notification operations, ensuring robust service integration.
- Updated documentation to include usage examples and configuration details for the new notification SDK.

pkg/config/config.go

@@ -65,6 +65,15 @@ type RateLimitConfig struct {
 	Burst             int `env:"RATE_LIMIT_BURST"`
 }
 
+type NotificationConfig struct {
+	BaseURL       string        `env:"NOTIFICATION_BASE_URL"`
+	Timeout       time.Duration `env:"NOTIFICATION_TIMEOUT"`
+	RetryAttempts int           `env:"NOTIFICATION_RETRY_ATTEMPTS"`
+	RetryDelay    time.Duration `env:"NOTIFICATION_RETRY_DELAY"`
+	EnableLogging bool          `env:"NOTIFICATION_ENABLE_LOGGING"`
+	UserAgent     string        `env:"NOTIFICATION_USER_AGENT"`
+}
+
 // LoadConfig loads configuration with priority: OS environment variables > .env file
 // OS environment variables take precedence over .env file values
 func LoadConfig[T any](path string, config T) (T, error) {