Enhance Notification Request Structure and Service Interface

- Updated the NotificationRequest struct to include new fields: Title, Type, Priority, and ScheduledAt, improving the flexibility and usability of notification requests.
- Implemented validation for the new ScheduledAt field to ensure it is a future timestamp or zero for immediate delivery.
- Refactored the NotificationService interface and SDK methods to accept a new Model struct, streamlining the parameters for sending notifications.
- Enhanced the builder pattern for constructing notification requests, adding methods for setting Title, Type, Priority, and ScheduledAt, promoting a fluent API design.
- Updated service methods for sending notifications (Email, SMS, Push, OTP) to utilize the new Model struct, ensuring consistency across notification types.

pkg/notification/entities.go

@@ -24,10 +24,14 @@ type NotificationMethods struct {
 
 // NotificationRequest represents the request structure for sending notifications
 type NotificationRequest struct {
-	EventType EventType           `json:"event_type" valid:"required,in(EMAIL|SMS|PUSH|OTP)"`
-	Message   string              `json:"message" valid:"required,length(1|1000)"`
-	Methods   NotificationMethods `json:"methods" valid:"required"`
-	UserID    string              `json:"user_id,omitempty" valid:"optional"`
+	UserID      string              `json:"user_id,omitempty" valid:"optional"`
+	Title       string              `json:"title" valid:"required"`
+	Message     string              `json:"message" valid:"required,length(1|1000)"`
+	Type        string              `json:"type" valid:"required,in(info|warning|alert|reject)"`
+	EventType   EventType           `json:"event_type" valid:"required,in(EMAIL|SMS|PUSH|OTP)"`
+	Priority    string              `json:"priority" valid:"required,in(low|medium|important)"`
+	ScheduledAt int64               `json:"scheduled_at"`
+	Methods     NotificationMethods `json:"methods" valid:"required"`
 }
 
 // NotificationResponse represents the successful response from notification service
@@ -67,6 +71,11 @@ func (nr *NotificationRequest) Validate() error {
 		}
 	}
 
+	// Validate scheduled_at: 0 means immediate delivery, otherwise must be future timestamp
+	if nr.ScheduledAt < 0 {
+		return ErrValidation{Field: "scheduled_at", Message: "scheduled_at cannot be negative"}
+	}
+
 	return nil
 }
 
@@ -101,3 +110,8 @@ func (nm *NotificationMethods) GetMethodValue(eventType EventType) string {
 		return ""
 	}
 }
+
+// IsImmediate returns true if the notification should be sent immediately (scheduled_at = 0)
+func (nr *NotificationRequest) IsImmediate() bool {
+	return nr.ScheduledAt == 0
+}