Remove MediatorGetOrContext; add ExecuteAsync overloads

Removed MediatorGetOrContext.cs, eliminating the fluent API for handling null or empty MediatR responses with custom exceptions. Added two ExecuteAsync overloads to FinalizeDocumentJob: one for processing a single EnvelopeDto and another for processing all envelopes with the EnvelopeCompletelySigned status.

EnvelopeGenerator.Application/Common/Extensions/MediatorGetOrContext.cs

@@ -1,77 +0,0 @@
-using DigitalData.Core.Exceptions;
-using MediatR;
-using System.Collections;
-
-namespace EnvelopeGenerator.Application.Common.Extensions;
-
-/// <summary>
-/// Holds a pending MediatR request and exposes <c>Throw…</c> methods that send the request
-/// and throw a chosen exception when the response is <c>null</c> or an empty collection.
-/// </summary>
-/// <typeparam name="TResponse">The expected response type.</typeparam>
-public readonly struct MediatorGetOrContext<TResponse>
-{
-    private readonly ISender _sender;
-    private readonly IRequest<TResponse?> _request;
-    private readonly CancellationToken _cancel;
-
-    internal MediatorGetOrContext(ISender sender, IRequest<TResponse?> request, CancellationToken cancel)
-    {
-        _sender = sender;
-        _request = request;
-        _cancel = cancel;
-    }
-
-    /// <summary>
-    /// Sends the request and throws the exception produced by <paramref name="exceptionFactory"/>
-    /// when the response is <c>null</c> or an empty collection.
-    /// </summary>
-    public async Task<TResponse> Throw(Func<Exception> exceptionFactory)
-    {
-        if (await _sender.Send(_request, _cancel) is TResponse res)
-        {
-            // string implements IEnumerable<char>, so "" would be treated as an empty collection without this guard.
-            if (res is not string && res is IEnumerable enumerable && !enumerable.Cast<object>().Any())
-                throw exceptionFactory();
-
-            return res;
-        }
-
-        throw exceptionFactory();
-    }
-
-    /// <summary>
-    /// Sends the request and throws <see cref="NotFoundException"/> when the response is <c>null</c> or an empty collection.
-    /// </summary>
-    public Task<TResponse> ThrowNotFound(string? message = null)
-        => Throw(() => new NotFoundException(message ?? $"The requested resource of type {typeof(TResponse).Name} was not found."));
-
-    /// <summary>
-    /// Sends the request and throws <see cref="InvalidOperationException"/> when the response is <c>null</c> or an empty collection.
-    /// </summary>
-    public Task<TResponse> ThrowInvalidOperation(string? message = null)
-        => Throw(() => new InvalidOperationException(message ?? $"The operation for {typeof(TResponse).Name} returned no result."));
-
-    /// <summary>
-    /// Sends the request and throws <see cref="BadRequestException"/> when the response is <c>null</c> or an empty collection.
-    /// </summary>
-    public Task<TResponse> ThrowBadRequest(string? message = null)
-        => Throw(() => new BadRequestException(message ?? $"The request for {typeof(TResponse).Name} is invalid."));
-}
-
-/// <summary>
-/// Extension methods for <see cref="ISender"/> that provide a fluent API for enforcing non-null responses.
-/// </summary>
-public static class MediatorGetOrContext
-{
-    /// <summary>
-    /// Begins a fluent chain that sends <paramref name="request"/> and lets you choose how to handle a <c>null</c> or empty response.
-    /// <para>Usage:</para>
-    /// <code>
-    /// await sender.GetOr(query).ThrowNotFound();
-    /// await sender.GetOr(query, cancel).Throw(() => new MyException());
-    /// </code>
-    /// </summary>
-    public static MediatorGetOrContext<TResponse> GetOr<TResponse>(this ISender sender, IRequest<TResponse?> request, CancellationToken cancel = default)
-        => new(sender, request, cancel);
-}