feat: add soft_delete_time and hard_delete_time object metadata fields

PiperOrigin-RevId: 609782289

google/storage/v2/storage.proto

@@ -2458,6 +2458,20 @@ message Object {
 
   // A user-specified timestamp set on an object.
   google.protobuf.Timestamp custom_time = 26;
+
+  // Output only. This is the time when the object became soft-deleted.
+  //
+  // Soft-deleted objects are only accessible if a soft_delete_policy is
+  // enabled. Also see hard_delete_time.
+  optional google.protobuf.Timestamp soft_delete_time = 28
+      [(google.api.field_behavior) = OUTPUT_ONLY];
+
+  // Output only. The time when the object will be permanently deleted.
+  //
+  // Only set when an object becomes soft-deleted with a soft_delete_policy.
+  // Otherwise, the object will not be accessible.
+  optional google.protobuf.Timestamp hard_delete_time = 29
+      [(google.api.field_behavior) = OUTPUT_ONLY];
 }
 
 // An access-control entry.