Refactor document retrieval endpoints and authorization

- Updated DocumentController to use class-level [Authorize] and method-level role-based authorization for sender and receiver endpoints.
- Replaced ReadEnvelopeReceiverQuery with ReadDocumentQuery for sender document retrieval; simplified response logic.
- Added a new endpoint for fully authenticated receivers to fetch documents by envelope ID from user claims.
- Refactored ReadDocumentQuery and handler to always return DocumentDto, throw NotFoundException when needed, and use _repo.Query.
- Cleaned up using directives and removed legacy error handling and logging.

EnvelopeGenerator.Application/Documents/Queries/ReadDocumentQuery.cs

@@ -4,6 +4,7 @@ using EnvelopeGenerator.Domain.Entities;
 using Microsoft.EntityFrameworkCore;
 using AutoMapper;
 using EnvelopeGenerator.Application.Common.Dto;
+using DigitalData.Core.Exceptions;
 
 namespace EnvelopeGenerator.Application.Documents.Queries;
 
@@ -12,14 +13,14 @@ namespace EnvelopeGenerator.Application.Documents.Queries;
 /// </summary>
 /// <param name="Id">The unique identifier of the document. Optional.</param>
 /// <param name="EnvelopeId">The identifier of the envelope associated with the document. Optional.</param>
-public record ReadDocumentQuery(int? Id = null, int? EnvelopeId = null) : IRequest<DocumentDto?>
+public record ReadDocumentQuery(int? Id = null, int? EnvelopeId = null) : IRequest<DocumentDto>
 {
 }
 
 /// <summary>
 /// Handles queries for reading <see cref="Document"/> data based on either the document ID or the envelope ID.
 /// </summary>
-public class ReadDocumentQueryHandler : IRequestHandler<ReadDocumentQuery, DocumentDto?>
+public class ReadDocumentQueryHandler : IRequestHandler<ReadDocumentQuery, DocumentDto>
 {
     /// <summary>
     /// TempRepo for accessing <see cref="Document"/> entities.
@@ -50,20 +51,19 @@ public class ReadDocumentQueryHandler : IRequestHandler<ReadDocumentQuery, Docum
     /// <exception cref="InvalidOperationException">
     /// Thrown when neither <see cref="ReadDocumentQuery.Id"/> nor <see cref="ReadDocumentQuery.EnvelopeId"/> is provided.
     /// </exception>
-    public async Task<DocumentDto?> Handle(ReadDocumentQuery query, CancellationToken cancel)
+    public async Task<DocumentDto> Handle(ReadDocumentQuery query, CancellationToken cancel)
     {
         if (query.Id is not null)
         {
-            var doc = await _repo.ReadOnly().Where(d => d.Id == query.Id).FirstOrDefaultAsync(cancel);
+            var doc = await _repo.Query.Where(d => d.Id == query.Id).FirstOrDefaultAsync(cancel);
             return _mapper.Map<DocumentDto>(doc);
         }            
         else if (query.EnvelopeId is not null)
         {
-            var doc = await _repo.ReadOnly().Where(d => d.EnvelopeId == query.EnvelopeId).FirstOrDefaultAsync(cancel);
+            var doc = await _repo.Query.Where(d => d.EnvelopeId == query.EnvelopeId).FirstOrDefaultAsync(cancel);
             return _mapper.Map<DocumentDto>(doc);
         }
 
-        throw new InvalidOperationException(
-            $"Invalid {nameof(ReadDocumentQuery)}: either {nameof(query.Id)} or {nameof(query.EnvelopeId)} must be provided.");
+        throw new NotFoundException();
     }
 }