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/notification/USAGE.md

@@ -0,0 +1,87 @@
+# Notification SDK - Quick Usage Guide
+
+## Installation
+The SDK is already part of your `tm` module. Import it as:
+```go
+import "tm/pkg/notification"
+```
+
+## Basic Setup
+```go
+// 1. Configuration
+config := notification.DefaultConfig()
+config.BaseURL = "http://127.0.0.1:9095" // Your notification service URL
+
+// 2. Logger (using project's logger)
+loggerConfig := &logger.Config{Level: "info", Format: "json", Output: "stdout"}
+projectLogger := logger.NewLogger(loggerConfig)
+loggerAdapter := &notification.LoggerAdapter{Logger: projectLogger}
+
+// 3. Create SDK
+sdk, err := notification.NewSDK(config, loggerAdapter)
+```
+
+## Environment Variables
+```bash
+export NOTIFICATION_BASE_URL="http://127.0.0.1:9095"
+export NOTIFICATION_TIMEOUT="30s"
+export NOTIFICATION_RETRY_ATTEMPTS="3"
+export NOTIFICATION_RETRY_DELAY="2s"
+export NOTIFICATION_ENABLE_LOGGING="true"
+```
+
+## Quick Examples
+
+### Simple Email
+```go
+err := sdk.QuickEmail(ctx, "user@example.com", "Hello!")
+```
+
+### Custom Notification
+```go
+request := &notification.NotificationRequest{
+    EventType: notification.EventTypeEmail,
+    Message:   "Hello Nima",
+    Methods: notification.NotificationMethods{
+        OTP:   "09143257416",
+        SMS:   "09143257416", 
+        Push:  "devicefsdgsdgsg6766sdgdsg",
+        Email: "nakhostin.nima1998@gmail.com",
+    },
+    UserID: "",
+}
+response, err := sdk.SendNotification(ctx, request)
+```
+
+### Fluent Builder
+```go
+response, err := sdk.NewBuilder().
+    SetEventType(notification.EventTypeEmail).
+    SetMessage("Hello Nima").
+    SetEmail("nakhostin.nima1998@gmail.com").
+    Send(ctx)
+```
+
+### Batch Operations
+```go
+requests := []*notification.NotificationRequest{...}
+batchResponse, err := sdk.SendBatch(ctx, requests)
+```
+
+## API Response
+- **Success**: `{"status": "Notification sent"}`
+- **Error**: `{"error": "error message"}`
+
+## Error Handling
+```go
+if err != nil {
+    switch e := err.(type) {
+    case notification.ErrHTTP:
+        // HTTP error (400, 500, etc.)
+    case notification.ErrValidation:
+        // Validation error
+    case notification.ErrRetryExhausted:
+        // All retry attempts failed
+    }
+}
+```