Add InstanceStorageMetrics struct to TMDS v4 response.

Author: Hoshank Mali

agent/vendor/github.com/aws/amazon-ecs-agent/ecs-agent/tmds/handlers/v4/state/response.go

@@ -36,6 +36,7 @@ type TaskResponse struct {
 	ServiceName             string                   `json:"ServiceName,omitempty"`
 	ClockDrift              *ClockDrift              `json:"ClockDrift,omitempty"`
 	EphemeralStorageMetrics *EphemeralStorageMetrics `json:"EphemeralStorageMetrics,omitempty"`
+	InstanceStorageMetrics  *InstanceStorageMetrics  `json:"InstanceStorageMetrics,omitempty"`
 	CredentialsID           string                   `json:"-"`
 	TaskNetworkConfig       *TaskNetworkConfig       `json:"-"`
 	FaultInjectionEnabled   bool                     `json:"FaultInjectionEnabled"`
@@ -90,6 +91,13 @@ type EphemeralStorageMetrics struct {
 	ReservedMiBs int64 `json:"Reserved"`
 }
 
+// InstanceStorageMetrics represents instance-level storage metrics exposed via TMDS.
+// Only DataFilesystemUtilization is exposed to customers. RootFilesystemUtilization
+// is collected internally but not included in the TMDS response.
+type InstanceStorageMetrics struct {
+	DataFilesystemUtilization float64 `json:"DataFilesystemUtilization"`
+}
+
 // ContainerResponse is the v4 Container response. It augments the v4 Network response
 // with the v2 container response object.
 type ContainerResponse struct {