Refactor DTOs for improved structure and documentation

Transitioned from records to classes for flexibility, added XML documentation for clarity, and updated property definitions to use standard getters and setters. Introduced the `required` keyword for essential properties, removed unnecessary constructors, and enhanced property descriptions for better readability. Additionally, overridden `GetHashCode` in `ReceiverReadDto` for proper collection behavior.

EnvelopeGenerator.Application/DTOs/Receiver/ReceiverUpdateDto.cs

@@ -3,5 +3,26 @@ using Microsoft.AspNetCore.Mvc;
 
 namespace EnvelopeGenerator.Application.DTOs.Receiver;
 
+/// <summary>
+/// Data Transfer Object for updating a receiver's information.
+/// </summary>
 [ApiExplorerSettings(IgnoreApi = true)]
-public record ReceiverUpdateDto(int Id, string? TotpSecretkey = null, DateTime? TfaRegDeadline = null) : IUnique<int>;
+public class ReceiverUpdateDto : IUnique<int>
+{
+    /// <summary>
+    /// Gets or sets the unique identifier of the receiver.
+    /// </summary>
+    public int Id { get; set; }
+
+    /// <summary>
+    /// Gets or sets the TOTP (Time-based One-Time Password) secret key.
+    /// Optional.
+    /// </summary>
+    public string? TotpSecretkey { get; set; }
+
+    /// <summary>
+    /// Gets or sets the deadline for two-factor authentication registration.
+    /// Optional.
+    /// </summary>
+    public DateTime? TfaRegDeadline { get; set; }
+}