fix #I9KL18 当前审核人审核通过后，下个审核人还没审核，当前审核人可以撤回

OpenAuth.WebApi/Controllers/FlowInstancesController.cs

@@ -167,6 +167,27 @@ namespace OpenAuth.WebApi.Controllers
             return response;
         }
 
+        /// <summary>
+        /// 撤销最后一个节点审批
+        /// </summary>
+        /// <returns></returns>
+        [HttpPost]
+        public Response UndoVerification([FromBody] UndoVerificationReq request)
+        {
+            var result = new Response();
+            try
+            {
+                _app.UndoVerification(request);
+            }
+            catch (Exception ex)
+            {
+                result.Code = 500;
+                result.Message = ex.InnerException?.Message ?? ex.Message;
+            }
+
+            return result;
+        }
+
         /// <summary>
         /// 加载列表
         /// </summary>
@@ -194,6 +215,9 @@ namespace OpenAuth.WebApi.Controllers
             return result;
         }
 
+
+
+
         public FlowInstancesController(FlowInstanceApp app) 
         {
             _app = app;