added resource validator and corrected documentation

Author: Divya-Singh1693

ibm/provider/provider.go

@@ -2169,8 +2169,9 @@ func Validator() validate.ValidatorDict {
 
 				// Added for Event Notifications
 
-				"ibm_en_smtp_configuration": eventnotification.ResourceIBMEnSMTPConfigurationValidator(),
-				"ibm_en_smtp_user":          eventnotification.ResourceIBMEnSMTPUserValidator(),
+				"ibm_en_smtp_configuration":       eventnotification.ResourceIBMEnSMTPConfigurationValidator(),
+				"ibm_en_smtp_user":                eventnotification.ResourceIBMEnSMTPUserValidator(),
+				"ibm_en_destination_custom_email": eventnotification.ResourceIBMEnEmailDestinationValidator(),
 
 				// Added for VMware as a Service
 				"ibm_vmaas_vdc":             vmware.ResourceIbmVmaasVdcValidator(),

ibm/service/eventnotification/resource_ibm_en_destination_custom_email.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/IBM-Cloud/terraform-provider-ibm/ibm/conns"
 	"github.com/IBM-Cloud/terraform-provider-ibm/ibm/flex"
+	"github.com/IBM-Cloud/terraform-provider-ibm/ibm/validate"
 	"github.com/IBM/go-sdk-core/v5/core"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
@@ -153,6 +154,23 @@ func ResourceIBMEnCustomEmailDestination() *schema.Resource {
 	}
 }
 
+func ResourceIBMEnEmailDestinationValidator() *validate.ResourceValidator {
+	validateSchema := make([]validate.ValidateSchema, 0)
+	validateSchema = append(validateSchema,
+		validate.ValidateSchema{
+			Identifier:                 "verification_type",
+			ValidateFunctionIdentifier: validate.ValidateAllowedStringValue,
+			Type:                       validate.TypeString,
+			Optional:                   true,
+			AllowedValues:              "spf,dkim",
+			MinValueLength:             1,
+		},
+	)
+
+	resourceValidator := validate.ResourceValidator{ResourceName: "ibm_en_destination_custom_email", Schema: validateSchema}
+	return &resourceValidator
+}
+
 func resourceIBMEnCustomEmailDestinationCreate(context context.Context, d *schema.ResourceData, meta interface{}) diag.Diagnostics {
 	enClient, err := meta.(conns.ClientSession).EventNotificationsApiV1()
 	if err != nil {

website/docs/r/en_destination_custom_email.html.markdown

@@ -17,7 +17,6 @@ resource "ibm_en_destination_custom_email" "custom_domain_en_destination" {
   instance_guid         = ibm_resource_instance.en_terraform_test_resource.guid
   name                  = "Custom Email EN Destination"
   type                  = "smtp_custom"
-  verification_type     = ""
   collect_failed_events = true
   description           = "Destination Custom Email for event notification"
     config {