Add converters from CICM Metadata to Aaru Metadata.

AaruMetadata/Checksum.cs

@@ -36,17 +36,24 @@
 // Copyright © 2011-2023 Natalia Portillo
 // ****************************************************************************/
 
-
-
 // ReSharper disable UnusedMember.Global
 // ReSharper disable ClassNeverInstantiated.Global
 
+using System;
+
 namespace Aaru.CommonTypes.AaruMetadata;
 
 public class Checksum
 {
     public ChecksumType Type  { get; set; }
     public string       Value { get; set; }
+
+    [Obsolete("Will be removed in Aaru 7")]
+    public static implicit operator Checksum(Schemas.ChecksumType cicm) => cicm is null ? null : new Checksum
+    {
+        Value = cicm.Value,
+        Type  = (ChecksumType)cicm.type
+    };
 }
 
 public enum ChecksumType