Fix missing creationDate in output (#18093)

Author: audunn

src/NetAppFiles/NetAppFiles/Helpers/BackupExtensions.cs

@@ -36,7 +36,8 @@ public static PSNetAppFilesBackup ConvertToPs(this Management.NetApp.Models.Back
                 ProvisioningState = backup.ProvisioningState,
                 Size = backup.Size,
                 VolumeName = backup.VolumeName,
-                UseExistingSnapshot = backup.UseExistingSnapshot
+                UseExistingSnapshot = backup.UseExistingSnapshot,
+                CreationDate = backup.CreationDate
             };
             return psBackup;
         }

src/NetAppFiles/NetAppFiles/Models/PSNetAppFilesBackup.cs

@@ -60,7 +60,7 @@ public class PSNetAppFilesBackup
         /// <remarks>
         /// The creation date of the backup
         /// </remarks>
-        public DateTime? CreationDate { get; }
+        public DateTime? CreationDate { get; set; }
 
         /// <summary>
         /// Gets Size