[CoinbasePro] Fix FundingRecord amount value to never be negative

xchange-core/src/main/java/org/knowm/xchange/dto/account/FundingRecord.java

@@ -68,6 +68,19 @@ public class FundingRecord implements Serializable {
 
   private final String toSubAccount;
 
+  /**
+   * Customizing amount method to always be positive. Rest of the builder code will be auto generated by Lombok.
+   *
+   */
+  public abstract static class FundingRecordBuilder<
+      C extends FundingRecord, B extends FundingRecordBuilder<C, B>> {
+
+    public B amount(BigDecimal amount) {
+      this.amount = amount == null ? null : amount.abs();
+      return self();
+    }
+  }
+
   @Deprecated // for backward compatibility.  Will be removed
   public String getExternalId() {
     return blockchainTransactionHash;