update： 添加支付回调

Runtime/GuruIAP/Runtime/Code/IAPServiceBase.cs

@@ -61,6 +61,7 @@ namespace Guru
 
         public event Action<string> OnBuyStart;
         public event Action<string, bool> OnBuyEnd;
+        public event Action<string, string> OnBuyFailed;
 
 #if UNITY_IOS
         /// <summary>
@@ -511,6 +512,8 @@ namespace Guru
             // 失败的处理逻辑
             OnPurchaseOver(false, info.Name);
             OnBuyEnd?.Invoke(info.Name, false);
+            // 失败原因
+            OnBuyFailed?.Invoke(info.Name, failureReason.ToString());
         }
         
         #endregion
@@ -564,7 +567,6 @@ namespace Guru
         protected abstract void OnPurchaseOver(bool success, string productName);
 
         #endregion
-
         
         #region 支付上报逻辑