Add Huobi GetAggregatedBalance api (#329)

Add Huobi GetAggregatedBalance api that returns the balances of all the
sub-account aggregated.

See also
  - https://huobiapi.github.io/docs/spot/v1/en/#get-the-aggregated-balance-of-all-sub-accounts-of-the-current-user

exchanges/huobi/huobi.go

@@ -42,6 +42,7 @@ const (
 	huobiTimestamp             = "common/timestamp"
 	huobiAccounts              = "account/accounts"
 	huobiAccountBalance        = "account/accounts/%s/balance"
+	huobiAggregatedBalance     = "subuser/aggregate-balance"
 	huobiOrderPlace            = "order/orders/place"
 	huobiOrderCancel           = "order/orders/%s/submitcancel"
 	huobiOrderCancelBatch      = "order/orders/batchcancel"
@@ -399,6 +400,29 @@ func (h *HUOBI) GetAccountBalance(accountID string) ([]AccountBalanceDetail, err
 	return result.AccountBalanceData.AccountBalanceDetails, err
 }
 
+// GetAggregatedBalance returns the balances of all the sub-account aggregated.
+func (h *HUOBI) GetAggregatedBalance() ([]AggregatedBalance, error) {
+	type response struct {
+		Response
+		AggregatedBalances []AggregatedBalance `json:"data"`
+	}
+
+	var result response
+
+	err := h.SendAuthenticatedHTTPRequest(
+		http.MethodGet,
+		huobiAggregatedBalance,
+		nil,
+		nil,
+		&result,
+	)
+
+	if result.ErrorMessage != "" {
+		return nil, errors.New(result.ErrorMessage)
+	}
+	return result.AggregatedBalances, err
+}
+
 // SpotNewOrder submits an order to Huobi
 func (h *HUOBI) SpotNewOrder(arg SpotNewOrderRequestParams) (int64, error) {
 	data := struct {

exchanges/huobi/huobi_test.go

@@ -210,6 +210,19 @@ func TestGetAccountBalance(t *testing.T) {
 	}
 }
 
+func TestGetAggregatedBalance(t *testing.T) {
+	t.Parallel()
+
+	if h.APIKey == "" || h.APISecret == "" || h.APIAuthPEMKey == "" {
+		t.Skip()
+	}
+
+	_, err := h.GetAggregatedBalance()
+	if err != nil {
+		t.Errorf("Test failed - Huobi GetAggregatedBalance: %s", err)
+	}
+}
+
 func TestSpotNewOrder(t *testing.T) {
 	t.Parallel()
 

exchanges/huobi/huobi_types.go

@@ -131,6 +131,12 @@ type AccountBalanceDetail struct {
 	Balance  float64 `json:"balance,string"`
 }
 
+// AggregatedBalance stores balances of all the sub-account
+type AggregatedBalance struct {
+	Currency string  `json:"currency"`
+	Balance  float64 `json:"balance,string"`
+}
+
 // CancelOrderBatch stores the cancel order batch data
 type CancelOrderBatch struct {
 	Success []string `json:"success"`