Correcting data type of properties in RejectWorkflowRequest from string to Guid

#45

Author: ziagham

src/FlowSynx.Client/Messages/Requests/Workflows/RejectWorkflowRequest.cs

@@ -2,7 +2,7 @@
 
 public class RejectWorkflowRequest
 {
-    public required string WorkflowId { get; set; }
-    public required string WorkflowExecutionId { get; set; }
-    public required string WorkflowExecutionApprovalId { get; set; }
+    public required Guid WorkflowId { get; set; }
+    public required Guid WorkflowExecutionId { get; set; }
+    public required Guid WorkflowExecutionApprovalId { get; set; }
 }