feat(ReadEnvelopeQuery): implement ReadEnvelopeQueryHandler with filtering support

- Added `ReadEnvelopeQueryHandler` to handle `ReadEnvelopeQuery`.
- Supports filtering envelopes by:
  - Included and ignored `EnvelopeStatus` values.
  - Minimum and maximum status.
  - Presence or absence of `DocResult`.
- Uses repository query extension methods and AutoMapper to map to `EnvelopeDto`.

EnvelopeGenerator.Application/Envelopes/Queries/ReadEnvelopeQuery.cs

@@ -2,6 +2,11 @@
 using EnvelopeGenerator.Domain.Constants;
 using EnvelopeGenerator.Application.Common.Query;
 using EnvelopeGenerator.Application.Common.Dto;
+using AutoMapper;
+using DigitalData.Core.Abstraction.Application.Repository;
+using EnvelopeGenerator.Application.Common.Extensions;
+using EnvelopeGenerator.Domain.Entities;
+using Microsoft.EntityFrameworkCore;
 
 namespace EnvelopeGenerator.Application.Envelopes.Queries;
 
@@ -71,4 +76,65 @@ public record EnvelopeStatusQuery
     /// Eine Liste von Statuswerten, die ignoriert werden werden.
     /// </summary>
     public EnvelopeStatus[]? Ignore { get; init; }
+}
+
+/// <summary>
+/// 
+/// </summary>
+public class ReadEnvelopeQueryHandler : IRequestHandler<ReadEnvelopeQuery, IEnumerable<EnvelopeDto>>
+{
+    private readonly IMapper _mapper;
+
+    private readonly IRepository<Envelope> _repo;
+
+    /// <summary>
+    /// 
+    /// </summary>
+    /// <param name="mapper"></param>
+    /// <param name="repo"></param>
+    public ReadEnvelopeQueryHandler(IMapper mapper, IRepository<Envelope> repo)
+    {
+        _mapper = mapper;
+        _repo = repo;
+    }
+
+    /// <summary>
+    /// 
+    /// </summary>
+    /// <param name="request"></param>
+    /// <param name="cancel"></param>
+    /// <returns></returns>
+    /// <exception cref="NotImplementedException"></exception>
+    public async Task<IEnumerable<EnvelopeDto>> Handle(ReadEnvelopeQuery request, CancellationToken cancel)
+    {
+        var q = _repo.Query.Where(request, notnull: false);
+
+        if (request.Status is EnvelopeStatusQuery statusQ)
+        {
+            // including status
+            if (statusQ.Include is EnvelopeStatus[] incStatus)
+                q = q.Where(e => incStatus.Contains(e.Status));
+
+            // ignoring status
+            if (statusQ.Ignore is EnvelopeStatus[] ignoreStatus)
+                q = q.Where(e => !ignoreStatus.Contains(e.Status));
+
+            // max status
+            if (statusQ.Max is EnvelopeStatus maxStatus)
+                q = q.Where(e => e.Status < maxStatus);
+
+            // min status
+            if (statusQ.Min is EnvelopeStatus minStatus)
+                q = q.Where(e => e.Status > minStatus);
+        }
+
+        if (request.HasDocResult is bool hasDocResult)
+            q = hasDocResult
+                ? q.Where(e => e.DocResult != null)
+                : q.Where(e => e.DocResult == null);
+
+        var envelopes = await q.ToListAsync(cancel);
+
+        return _mapper.Map<IEnumerable<EnvelopeDto>>(envelopes);
+    }
 }