rate limiting e cpf masking

OpenCand.Core/Utils/CpfMasking.cs

@@ -0,0 +1,21 @@
+namespace OpenCand.Core.Utils
+{
+    public static class CpfMasking
+    {
+        /// <summary>
+        /// Masks a CPF number by replacing the middle 3 digits with '*'
+        /// </summary>
+        /// <param name="cpf">The CPF number to mask.</param>
+        /// <returns>The masked CPF number.</returns>
+        public static string MaskCpf(string cpf)
+        {
+            if (string.IsNullOrEmpty(cpf) || cpf.Length != 11)
+            {
+                return cpf;
+            }
+
+            // Mask the middle 3 digits
+            return $"{cpf.Substring(0, 3)}***{cpf.Substring(6)}";
+        }
+    }
+}