Add CloseAsync method and WorkflowClosing entity

Introduced a new method `CloseAsync` in the `IWorkflowRepository`
interface to handle workflow item closure and return a procedure
result. Added a new class `WorkflowClosing` in `WorkflowClosing.cs`
as a sealed class inheriting from `ProcedureResultBase`.

Updated `TaskFlowDbContext` to include a `DbSet<WorkflowClosing>`
for keyless workflow close procedure results. Configured the
`WorkflowClosing` entity in `OnModelCreating` with specific
column mappings and a maximum length for the `Result` property.

src/core/DigitalData.TaskFlow.Application/Common/Interfaces/IWorkflowRepository.cs

@@ -14,4 +14,24 @@ public interface IWorkflowRepository : IRepository
     /// <param name="cancellationToken">Cancellation token.</param>
     /// <returns>Workflow data grouped by source.</returns>
     Task<Workflow?> GetByWisagIdAsync(int wisagId, CancellationToken cancellationToken);
+
+    /// <summary>
+    /// Closes a workflow item and returns procedure result code/message.
+    /// </summary>
+    /// <param name="userId">Internal user identifier expected by the procedure.</param>
+    /// <param name="source">Source system identifier.</param>
+    /// <param name="processId">Process identifier.</param>
+    /// <param name="closingMethodId">Closing method identifier.</param>
+    /// <param name="comment">Optional comment.</param>
+    /// <param name="rejectionReasonId">Optional rejection reason identifier.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>Close operation result.</returns>
+    Task<WorkflowClosing?> CloseAsync(
+        int userId,
+        string source,
+        long processId,
+        int closingMethodId,
+        string? comment,
+        byte? rejectionReasonId,
+        CancellationToken cancellationToken);
 }

src/core/DigitalData.TaskFlow.Domain/ProcedureResults/WorkflowClosing.cs

@@ -0,0 +1,5 @@
+namespace DigitalData.TaskFlow.Domain.ProcedureResults;
+
+public sealed class WorkflowClosing : ProcedureResultBase
+{
+}

src/infrastructure/DigitalData.TaskFlow.Infrastructure/Persistence/TaskFlowDbContext.cs

@@ -18,6 +18,11 @@ public sealed class TaskFlowDbContext(DbContextOptions<TaskFlowDbContext> option
     /// </summary>
     public DbSet<Document> Documents => Set<Document>();
 
+    /// <summary>
+    /// Gets the keyless result model used for workflow close procedure results.
+    /// </summary>
+    public DbSet<WorkflowClosing> WorkflowClosings => Set<WorkflowClosing>();
+
     protected override void OnModelCreating(ModelBuilder modelBuilder)
     {
         base.OnModelCreating(modelBuilder);
@@ -37,5 +42,13 @@ public sealed class TaskFlowDbContext(DbContextOptions<TaskFlowDbContext> option
             entity.Property(x => x.Code).HasColumnName("CODE").HasColumnType("int");
             entity.Property(x => x.Result).HasColumnName("RESULT").HasColumnType("nvarchar(max)");
         });
+
+        modelBuilder.Entity<WorkflowClosing>(entity =>
+        {
+            entity.HasNoKey();
+            entity.ToView(null);
+            entity.Property(x => x.Code).HasColumnName("CODE").HasColumnType("int");
+            entity.Property(x => x.Result).HasColumnName("RESULT").HasColumnType("nvarchar(400)");
+        });
     }
 }