[Kucoin] Enforce fields as string as per api docs

Author: ivansolomonoff

xchange-examples/src/main/java/org/knowm/xchange/examples/kucoin/trade/KucoinTradeRawDemo.java

@@ -209,8 +209,8 @@ private static void raw(KucoinTradeServiceRaw tradeService) throws Exception {
 
     OrderCreateApiRequest limitOrder =
         OrderCreateApiRequest.builder()
-            .size(AMOUNT)
-            .price(PRICE)
+            .size(AMOUNT.toPlainString())
+            .price(PRICE.toPlainString())
             .side("sell")
             .symbol(SYMBOL)
             .type("limit")

xchange-kucoin/src/main/java/org/knowm/xchange/kucoin/KucoinAdapters.java

@@ -292,7 +292,7 @@ public static UserTrade adaptHistOrder(HistOrdersResponse histOrder) {
   public static OrderCreateApiRequest adaptLimitOrder(LimitOrder limitOrder) {
     return ((OrderCreateApiRequest.OrderCreateApiRequestBuilder) adaptOrder(limitOrder))
         .type("limit")
-        .price(limitOrder.getLimitPrice())
+        .price(limitOrder.getLimitPrice().toPlainString())
         .postOnly(limitOrder.hasFlag(POST_ONLY))
         .hidden(limitOrder.hasFlag(HIDDEN))
         .iceberg(limitOrder.hasFlag(ICEBERG))
@@ -302,8 +302,8 @@ public static OrderCreateApiRequest adaptLimitOrder(LimitOrder limitOrder) {
   public static OrderCreateApiRequest adaptStopOrder(StopOrder stopOrder) {
     return ((OrderCreateApiRequest.OrderCreateApiRequestBuilder) adaptOrder(stopOrder))
         .type(stopOrder.getLimitPrice() == null ? "market" : "limit")
-        .price(stopOrder.getLimitPrice())
-        .stopPrice(stopOrder.getStopPrice())
+        .price(stopOrder.getLimitPrice().toPlainString())
+        .stopPrice(stopOrder.getStopPrice().toPlainString())
         .build();
   }
 
@@ -315,11 +315,11 @@ public static OrderCreateApiRequest adaptMarketOrder(MarketOrder marketOrder) {
     // on buy order amount corresponds to counter currency
     if (marketOrder.getType() == BID) {
       builder.size(null);
-      builder.funds(marketOrder.getOriginalAmount());
+      builder.funds(marketOrder.getOriginalAmount().toPlainString());
     }
     // on sell order amount corresponds to base currency
     else if (marketOrder.getType() == ASK) {
-      builder.size(marketOrder.getOriginalAmount());
+      builder.size(marketOrder.getOriginalAmount().toPlainString());
       builder.funds(null);
     }
 
@@ -352,7 +352,7 @@ private static Object adaptOrder(Order order) {
     }
     return request
         .symbol(adaptCurrencyPair((CurrencyPair) order.getInstrument()))
-        .size(order.getOriginalAmount())
+        .size(order.getOriginalAmount().toPlainString())
         .side(adaptSide(order.getType()));
   }
 

xchange-kucoin/src/main/java/org/knowm/xchange/kucoin/dto/request/OrderCreateApiRequest.java

@@ -38,15 +38,15 @@ public class OrderCreateApiRequest {
   private final String stop;
 
   /** Trigger price for the stop order. Null for regular orders. */
-  private final BigDecimal stopPrice;
+  private final String stopPrice;
 
   // Common fields
 
   /** [limit order] Price per base currency. */
-  private final BigDecimal price;
+  private final String price;
 
   /** [limit order] Amount of base currency to buy or sell. */
-  private final BigDecimal size;
+  private final String size;
 
   /** [limit order] Time in force strategy: GTC, GTT, IOC, or FOK (default is GTC). */
   @Builder.Default private final String timeInForce = "GTC";
@@ -64,11 +64,11 @@ public class OrderCreateApiRequest {
   private final boolean iceberg;
 
   /** [limit order] The maximum visible size of an iceberg order. */
-  private final BigDecimal visibleSize;
+  private final String visibleSize;
 
   /**
    * [market order] The amount of quote currency to spend.
    * size and funds are mutually exclusive.
    */
-  private final BigDecimal funds;
+  private final String funds;
 }

xchange-kucoin/src/test/java/org/knowm/xchange/kucoin/KucoinAdaptersTest.java

@@ -15,7 +15,7 @@ class KucoinAdaptersTest {
   void adapt_market_buy_order() {
     OrderCreateApiRequest expected =
         OrderCreateApiRequest.builder()
-            .funds(new BigDecimal("15"))
+            .funds(new BigDecimal("15").toPlainString())
             .clientOid("abc")
             .side("buy")
             .symbol("BTC-USDT")
@@ -37,7 +37,7 @@ void adapt_market_buy_order() {
   void adapt_market_sell_order() {
     OrderCreateApiRequest expected =
         OrderCreateApiRequest.builder()
-            .size(new BigDecimal("0.002"))
+            .size(new BigDecimal("0.002").toPlainString())
             .clientOid("abc")
             .side("sell")
             .symbol("BTC-USDT")