Added Validation logics

Toolkit.Foundation/ValidationRule.cs

@@ -0,0 +1,27 @@
+namespace Toolkit.Foundation;
+
+public class ValidationRule
+{
+    public ValidationRule(Func<bool> validation,
+        string message)
+    {
+        Validation = validation;
+        Message = new Func<string>(() => message);
+    }
+
+    public ValidationRule(Func<bool> validation)
+    {
+        Validation = validation;
+    }
+
+    public ValidationRule(Func<bool> validation,
+        Func<string> message)
+    {
+        Validation = validation;
+        Message = message;
+    }
+
+    public Func<string>? Message { get; }
+
+    public Func<bool>? Validation { get; }
+}