统一AssignmentStatus字段类型，新建枚举，对应状态

QYZH.InteractiveMagazine.Models/Entity/JournalPageTaskUserAnswer.cs

@@ -231,6 +231,6 @@ namespace QYZH.InteractiveMagazine.Models.Entity
         /// Default:
         /// Nullable:True
         /// </summary>
-        public string AssignmentStatus { get; set; }
+        public int AssignmentStatus { get; set; }
     }
 }