加入积分系统，将充值与积分关联

src/main/java/com/ai/da/service/CreditsService.java

@@ -0,0 +1,16 @@
+package com.ai.da.service;
+
+public interface CreditsService {
+
+    void initCredits();
+
+    Boolean buyCredits(Long accountId, Integer quantity);
+
+    void creditsIncrease(Long accountId, String event);
+
+    void creditsDecrease(Long accountId, String event);
+
+    String getCredits();
+
+    void creditsRefund(Long accountId, Integer quantity);
+}