[MM-58159] Add admin setting for notification monitoring alongside feature flag (#26979)

* [MM-58159] Add admin setting for notification monitoring alongside feature flag

* Use helper function

server/public/model/config.go

@@ -980,10 +980,11 @@ func (s *ClusterSettings) SetDefaults() {
 }
 
 type MetricsSettings struct {
-	Enable              *bool   `access:"environment_performance_monitoring,write_restrictable,cloud_restrictable"`
-	BlockProfileRate    *int    `access:"environment_performance_monitoring,write_restrictable,cloud_restrictable"`
-	ListenAddress       *string `access:"environment_performance_monitoring,write_restrictable,cloud_restrictable"` // telemetry: none
-	EnableClientMetrics *bool   `access:"environment_performance_monitoring,write_restrictable,cloud_restrictable"`
+	Enable                    *bool   `access:"environment_performance_monitoring,write_restrictable,cloud_restrictable"`
+	BlockProfileRate          *int    `access:"environment_performance_monitoring,write_restrictable,cloud_restrictable"`
+	ListenAddress             *string `access:"environment_performance_monitoring,write_restrictable,cloud_restrictable"` // telemetry: none
+	EnableClientMetrics       *bool   `access:"environment_performance_monitoring,write_restrictable,cloud_restrictable"`
+	EnableNotificationMetrics *bool   `access:"environment_performance_monitoring,write_restrictable,cloud_restrictable"`
 }
 
 func (s *MetricsSettings) SetDefaults() {
@@ -1002,6 +1003,10 @@ func (s *MetricsSettings) SetDefaults() {
 	if s.EnableClientMetrics == nil {
 		s.EnableClientMetrics = NewBool(true)
 	}
+
+	if s.EnableNotificationMetrics == nil {
+		s.EnableNotificationMetrics = NewBool(true)
+	}
 }
 
 type ExperimentalSettings struct {