Implement phone number validation for customer and user registration and updates

Added functionality to check for existing customers and users by phone number during registration and updates. Updated the handler, service, and repository layers to include phone number checks, ensuring unique phone numbers across customers and users.

internal/customer/service.go

@@ -95,6 +95,13 @@ func (s *customerService) Register(ctx context.Context, form *CreateCustomerForm
 		return nil, errors.New("customer with this username already exists")
 	}
 
+	if form.Phone != nil && *form.Phone != "" {
+		existingCustomer, _ = s.repository.GetByPhone(ctx, *form.Phone)
+		if existingCustomer != nil {
+			return nil, errors.New("customer with this phone number already exists")
+		}
+	}
+
 	// Check validator
 	if !s.validator.IsValidUsername(form.Username) {
 		return nil, errors.New("invalid username format")
@@ -373,6 +380,12 @@ func (s *customerService) Update(ctx context.Context, id string, form *UpdateCus
 	}
 
 	if form.Phone != nil && (customer.Phone == nil || *form.Phone != *customer.Phone) {
+		if *form.Phone != "" {
+			existingCustomer, _ := s.repository.GetByPhone(ctx, *form.Phone)
+			if existingCustomer != nil && existingCustomer.ID.Hex() != id {
+				return nil, errors.New("customer with this phone number already exists")
+			}
+		}
 		customer.Phone = form.Phone
 		infoChanged = true
 	}