feat(EnvelopeReceiverControler): add test endpoint for ReadEnvelopeReceiverQuery

EnvelopeGenerator.Application/EnvelopeReceivers/Queries/ReadEnvelopeReceiverQuery.cs

@@ -42,7 +42,7 @@ namespace EnvelopeGenerator.Application.EnvelopeReceivers.Queries;
 /// Die Antwort enthält Details wie den StatusQ, die Zuordnung zwischen Umschlag und Empfänger 
 /// sowie zusätzliche Metadaten.
 /// </remarks>
-public record ReadEnvelopeReceiverQuery : IRequest<EnvelopeReceiverDto>
+public record ReadEnvelopeReceiverQuery : IRequest<EnvelopeReceiverDto?>
 {
     /// <summary>
     /// 

EnvelopeGenerator.Application/EnvelopeReceivers/Queries/ReadEnvelopeReceiverQueryHandler.cs

@@ -10,7 +10,7 @@ namespace EnvelopeGenerator.Application.EnvelopeReceivers.Queries;
 /// <summary>
 /// 
 /// </summary>
-public class ReadEnvelopeReceiverQueryHandler : IRequestHandler<ReadEnvelopeReceiverQuery, EnvelopeReceiverDto>
+public class ReadEnvelopeReceiverQueryHandler : IRequestHandler<ReadEnvelopeReceiverQuery, EnvelopeReceiverDto?>
 {
     private readonly IRepository<EnvelopeReceiver> _repo;
 
@@ -20,6 +20,7 @@ public class ReadEnvelopeReceiverQueryHandler : IRequestHandler<ReadEnvelopeRece
     /// 
     /// </summary>
     /// <param name="envelopeReceiver"></param>
+    /// <param name="mapper"></param>
     public ReadEnvelopeReceiverQueryHandler(IRepository<EnvelopeReceiver> envelopeReceiver, IMapper mapper)
     {
         _repo = envelopeReceiver;
@@ -33,7 +34,7 @@ public class ReadEnvelopeReceiverQueryHandler : IRequestHandler<ReadEnvelopeRece
     /// <param name="cancel"></param>
     /// <returns></returns>
     /// <exception cref="NotImplementedException"></exception>
-    public async Task<EnvelopeReceiverDto> Handle(ReadEnvelopeReceiverQuery request, CancellationToken cancel)
+    public async Task<EnvelopeReceiverDto?> Handle(ReadEnvelopeReceiverQuery request, CancellationToken cancel)
     {
         var q = _repo.Read();
 
@@ -81,7 +82,6 @@ public class ReadEnvelopeReceiverQueryHandler : IRequestHandler<ReadEnvelopeRece
                         .Include(er => er.Receiver)
                         .FirstOrDefaultAsync(cancel);
 
-        var dto = _mapper.Map<EnvelopeReceiverDto>(er);
-        return dto;
+        return er is null ? null : _mapper.Map<EnvelopeReceiverDto>(er);
     } 
 }