Rename SignatureController to DocReceiverElementController

The class `SignatureController` has been renamed to `DocReceiverElementController` to better reflect its purpose. The constructor and its XML documentation have been updated accordingly. The `[Authorize]`, `[ApiController]`, and `[Route]` attributes remain unchanged. A `TODO` comment has been added to indicate future updates for using a signature query.

EnvelopeGenerator.API/Controllers/DocReceiverElementController.cs

@@ -0,0 +1,57 @@
+using EnvelopeGenerator.API.Extensions;
+using EnvelopeGenerator.Application.Common.Dto;
+using EnvelopeGenerator.Application.Common.Extensions;
+using EnvelopeGenerator.Application.Documents.Queries;
+using EnvelopeGenerator.Domain.Constants;
+using MediatR;
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+
+namespace EnvelopeGenerator.API.Controllers;
+
+/// <summary>
+/// 
+/// </summary>
+[Authorize(Policy = AuthPolicy.Receiver)]
+[ApiController]
+[Route("api/[controller]")]
+public class DocReceiverElementController : ControllerBase
+{
+    private readonly IMediator _mediator;
+
+    /// <summary>
+    /// Initializes a new instance of <see cref="DocReceiverElementController"/>.
+    /// </summary>
+    public DocReceiverElementController(IMediator mediator)
+    {
+        _mediator = mediator;
+    }
+
+    //TODO: update to use signature query
+    /// <summary>
+    /// 
+    /// </summary>
+    /// <param name="envelopeKey"></param>
+    /// <param name="cancel"></param>
+    /// <returns></returns>
+    [Authorize(Policy = AuthPolicy.Receiver)]
+    [HttpGet("{envelopeKey}")]
+    public async Task<IActionResult> Get(string envelopeKey, CancellationToken cancel)
+    {
+        int envelopeId = User.EnvelopeId();
+
+        int receiverId = User.ReceiverId();
+
+        var doc = await _mediator.Send(new ReadDocumentQuery() { EnvelopeId = envelopeId }, cancel);
+
+        if (doc.Elements is not IEnumerable<DocReceiverElementDto> docSignatures)
+            return NotFound("Document is empty.");
+
+        var rcvSignatures = docSignatures.Where(s => s.ReceiverId == receiverId).ToList();
+
+        if (rcvSignatures is null)
+            return NotFound("No signatures found for the current receiver.");
+        else
+            return Ok(rcvSignatures);
+    }
+}