exchanges/futures: Implement open interest (#1417)

* adds open interest to exchanges

* ADDS TESTING YEAH

* New endpoints, BTSE, RPCS, cached

* slight design change, begin gateio

You will need to get cached for
each exchange that supports it

* gateio, huobi, rpc

* fix up kraken, cache retrieval

* okx, gateio

* finalising all implementations and tests

* definitely my final ever commit on this

* Well, well, well

* final v2

* quick fix of bug

* test coverage, assert notempty, test helper

Added a new testhelper for currency
management because its very annoying
in a parallel test setting which wastes
so much space otherwise

* minimises REST requests for Open Interest

* types.Number merge misses

* Minimises Kraken REST calls

* len change, value -> pointer receiver

* further fixup

* fixes gateio, batch calculates open interest

* single gateio, lint const fixes

* rejig and more thorough oi for huobi

* formatting expansion

* minor fix for handling expiring contracts

* rm unused Binance strings

* add bybit support, fix bybit issues

* oopsie doopsie, dont look at my whoopsie

* Fix issue, remove feature

* move an irrelevant function for the pr

* mini bybit upgrades

* fixes cli request bug

exchanges/ticker/ticker_test.go

@@ -10,7 +10,9 @@ import (
 	"testing"
 	"time"
 
+	"github.com/gofrs/uuid"
 	"github.com/stretchr/testify/assert"
+	"github.com/thrasher-corp/gocryptotrader/common/key"
 	"github.com/thrasher-corp/gocryptotrader/currency"
 	"github.com/thrasher-corp/gocryptotrader/dispatch"
 	"github.com/thrasher-corp/gocryptotrader/exchanges/asset"
@@ -448,3 +450,44 @@ func TestGetAssociation(t *testing.T) {
 
 	service.mux = cpyMux
 }
+
+func TestGetExchangeTickersPublic(t *testing.T) {
+	_, err := GetExchangeTickers("")
+	assert.ErrorIs(t, err, errExchangeNameIsEmpty)
+}
+
+func TestGetExchangeTickers(t *testing.T) {
+	t.Parallel()
+	s := Service{
+		Tickers:  make(map[key.ExchangePairAsset]*Ticker),
+		Exchange: make(map[string]uuid.UUID),
+	}
+
+	_, err := s.getExchangeTickers("")
+	assert.ErrorIs(t, err, errExchangeNameIsEmpty)
+
+	_, err = s.getExchangeTickers("test")
+	assert.ErrorIs(t, err, errExchangeNotFound)
+
+	s.Tickers[key.ExchangePairAsset{
+		Exchange: "test",
+		Base:     currency.XBT.Item,
+		Quote:    currency.DOGE.Item,
+		Asset:    asset.Futures,
+	}] = &Ticker{
+		Price: Price{
+			Pair:         currency.NewPair(currency.XBT, currency.DOGE),
+			ExchangeName: "test",
+			AssetType:    asset.Futures,
+			OpenInterest: 1337,
+		},
+	}
+	s.Exchange["test"] = uuid.Must(uuid.NewV4())
+
+	resp, err := s.getExchangeTickers("test")
+	assert.NoError(t, err)
+	if len(resp) != 1 {
+		t.Fatal("unexpected length")
+	}
+	assert.Equal(t, resp[0].OpenInterest, 1337.0)
+}