feat(domain): add close workflow outcome semantics

src/core/DigitalData.TaskFlow.Domain/Closing/CloseWorkflowOutcome.cs

@@ -0,0 +1,32 @@
+namespace DigitalData.TaskFlow.Domain.Closing;
+
+/// <summary>
+/// Defines business outcomes of a close workflow attempt.
+/// </summary>
+public enum CloseWorkflowOutcome
+{
+    /// <summary>
+    /// Workflow can be closed successfully.
+    /// </summary>
+    Closed = 0,
+
+    /// <summary>
+    /// Caller has no access to the requested workflow.
+    /// </summary>
+    NoAccess = 1,
+
+    /// <summary>
+    /// Workflow process was not found.
+    /// </summary>
+    NotFound = 2,
+
+    /// <summary>
+    /// Workflow is already closed and cannot be closed again.
+    /// </summary>
+    AlreadyClosed = 3,
+
+    /// <summary>
+    /// Closing cannot be completed yet because write integration is not finalized.
+    /// </summary>
+    NotImplemented = 4
+}

src/core/DigitalData.TaskFlow.Domain/Closing/CloseWorkflowResult.cs

@@ -14,4 +14,9 @@ public sealed record CloseWorkflowResult
     /// Gets a value indicating whether the process was closed successfully.
     /// </summary>
     public required bool IsClosed { get; init; }
+
+    /// <summary>
+    /// Gets the business outcome of the close request.
+    /// </summary>
+    public CloseWorkflowOutcome Outcome { get; init; } = CloseWorkflowOutcome.Closed;
 }