refactor(Extensions): move to common

EnvelopeGenerator.Application/Common/Extensions/EncodingExtensions.cs

@@ -0,0 +1,38 @@
+using System.Text;
+
+namespace EnvelopeGenerator.Application.Common.Extensions;
+
+/// <summary>
+/// Provides extension methods for decoding and extracting information from an envelope receiver ID.
+/// </summary>
+public static class EncodingExtensions
+{
+    /// <summary>
+    /// 
+    /// </summary>
+    /// <param name="readOnlyId"></param>
+    /// <returns></returns>
+    public static string ToEnvelopeKey(this long readOnlyId)
+    {
+        //The random number is used as a salt to increase security but it is not saved in the database.
+        string combinedString = $"{Random.Shared.Next()}::{readOnlyId}::{Random.Shared.Next()}";
+        byte[] bytes = Encoding.UTF8.GetBytes(combinedString);
+        string base64String = Convert.ToBase64String(bytes);
+
+        return base64String;
+    }
+
+    /// <summary>
+    /// 
+    /// </summary>
+    /// <param name="input"></param>
+    /// <returns></returns>
+    public static string ToEnvelopeKey(this (string envelopeUuid, string receiverSignature) input)
+    {
+        string combinedString = $"{input.envelopeUuid}::{input.receiverSignature}";
+        byte[] bytes = Encoding.UTF8.GetBytes(combinedString);
+        string base64String = Convert.ToBase64String(bytes);
+
+        return base64String;
+    }
+}