Made ObjectHash static, add GetStringSignature

StabilityMatrix.Core/Helper/ObjectHash.cs

@@ -1,9 +1,10 @@
-using System.Text;
+using System.Security.Cryptography;
+using System.Text;
 using System.Text.Json;
 
 namespace StabilityMatrix.Core.Helper;
 
-public class ObjectHash
+public static class ObjectHash
 {
     /// <summary>
     /// Return a GUID based on the MD5 hash of the JSON representation of the object.
@@ -16,4 +17,25 @@ public class ObjectHash
         var hash = md5.ComputeHash(bytes);
         return new Guid(hash);
     }
+
+    /// <summary>
+    /// Return a short Sha256 signature of a string
+    /// </summary>
+    public static string GetStringSignature(string? str)
+    {
+        if (str is null)
+        {
+            return "null";
+        }
+
+        if (string.IsNullOrEmpty(str))
+        {
+            return "";
+        }
+
+        var bytes = Encoding.UTF8.GetBytes(str);
+        var hash = Convert.ToBase64String(SHA256.HashData(bytes));
+
+        return $"[..{str.Length}, {hash[..7]}]";
+    }
 }