为WxPayUnifiedOrderV3Result.AppResult的partnerId和prepayId添加@SerializedName注解，修复与微信官方API字段名不一致问题

Agent-Logs-Url: https://github.com/binarywang/WxJava/sessions/099513d0-4cde-45a3-850c-1afec934741c

Co-authored-by: binarywang <1343140+binarywang@users.noreply.github.com>

weixin-java-pay/src/main/java/com/github/binarywang/wxpay/bean/result/WxPayUnifiedOrderV3Result.java

@@ -110,7 +110,9 @@ public class WxPayUnifiedOrderV3Result implements Serializable {
     private static final long serialVersionUID = 5465773025172875110L;
 
     private String appid;
+    @SerializedName("partnerid")
     private String partnerId;
+    @SerializedName("prepayid")
     private String prepayId;
     /**
      * 由于package为java保留关键字，因此改为packageValue，序列化时会自动转换为package字段名

weixin-java-pay/src/test/java/com/github/binarywang/wxpay/bean/result/WxPayUnifiedOrderV3ResultTest.java

@@ -248,6 +248,13 @@ public class WxPayUnifiedOrderV3ResultTest {
     Assert.assertTrue(jsonObject.has("package"), "JSON中应该包含package字段");
     Assert.assertFalse(jsonObject.has("packageValue"), "JSON中不应该包含packageValue字段");
     Assert.assertEquals(jsonObject.get("package").getAsString(), "Sign=WXPay");
+    // 验证JSON序列化后partnerid和prepayid字段名为全小写（微信官方要求）
+    Assert.assertTrue(jsonObject.has("partnerid"), "JSON中应该包含partnerid字段");
+    Assert.assertFalse(jsonObject.has("partnerId"), "JSON中不应该包含驼峰的partnerId字段");
+    Assert.assertEquals(jsonObject.get("partnerid").getAsString(), testMchId);
+    Assert.assertTrue(jsonObject.has("prepayid"), "JSON中应该包含prepayid字段");
+    Assert.assertFalse(jsonObject.has("prepayId"), "JSON中不应该包含驼峰的prepayId字段");
+    Assert.assertEquals(jsonObject.get("prepayid").getAsString(), testPrepayId);
   }
 
   @Test(expectedExceptions = IllegalArgumentException.class,