Refactor DTOs to classes with enhanced properties

Changed `EnvelopeReceiverReadOnlyDto` and `EnvelopeReceiverReadOnlyUpdateDto` from records to classes, converting properties to standard get/set accessors and adding documentation comments. Introduced a default value for `ChangedWhen` in `EnvelopeReceiverReadOnlyUpdateDto`.

Modified `ReceiverCreateDto` to a class structure, updating properties to use init-only accessors and encapsulating SHA256 hash logic in a private field. Retained the `AddedWhen` property with its default value.

EnvelopeGenerator.Application/DTOs/Receiver/ReceiverCreateDto.cs

@@ -3,21 +3,30 @@ using System.ComponentModel.DataAnnotations;
 using System.Security.Cryptography;
 using System.Text;
 
-namespace EnvelopeGenerator.Application.DTOs.Receiver
-{
-    [ApiExplorerSettings(IgnoreApi = true)]
-    public record ReceiverCreateDto([EmailAddress] string EmailAddress, string? TotpSecretkey = null)
-    {
-        public string Signature => sha256HexOfMail.Value;
+namespace EnvelopeGenerator.Application.DTOs.Receiver;
 
-        private readonly Lazy<string> sha256HexOfMail = new(() =>
+[ApiExplorerSettings(IgnoreApi = true)]
+public record ReceiverCreateDto
+{
+    public ReceiverCreateDto()
+    {
+        _sha256HexOfMail = new(() =>
         {
             var bytes_arr = Encoding.UTF8.GetBytes(EmailAddress.ToUpper());
             var hash_arr = SHA256.HashData(bytes_arr);
             var hexa_str = BitConverter.ToString(hash_arr);
             return hexa_str.Replace("-", string.Empty);
         });
+    }
 
-        public DateTime AddedWhen { get; } = DateTime.Now;
-    };
-}
+    [EmailAddress]
+    public string EmailAddress { get; init; }
+
+    public string? TotpSecretkey { get; init; }
+
+    public string Signature => _sha256HexOfMail.Value;
+
+    private readonly Lazy<string> _sha256HexOfMail;
+
+    public DateTime AddedWhen { get; } = DateTime.Now;
+};