codebase: Cleanup various things (#1935)

* codebase: Rid base64/hex to string common funcs

* codebase: Rid local scope variable usage and other improvements

* codebase: Refactor currency pair usage across multiple exchanges

- Updated HitBTC tests to use the new currency pair format.
- Modified Kraken futures types to use currency.Pair instead of string for Symbol.
- Adjusted Kraken wrapper methods to handle currency pairs correctly.
- Refined OKX tests and types to utilize currency.Pair for instrument IDs.
- Enhanced Poloniex tests to consistently use predefined currency pairs.
- Streamlined order and orderbook tests to replace string pairs with currency.NewBTCUSD().
- Improved Yobit tests to utilize a standardized currency pair format.
- Updated validator wrapper to use currency pairs directly instead of string conversions.

* codebase: Use types.Number where possible

* refactor: update PayoutFee type to types.Number for consistency

* Refactor: Remove crypto functions to use standard library and other minor changes

- Removed custom crypto functions for SHA256, SHA512, and MD5 from the common/crypto package.
- Replaced usages of removed functions with standard library implementations in various files including:
  - cmd/websocket_client/main.go
  - engine/apiserver.go
  - exchanges/kraken/kraken.go
  - exchanges/lbank/lbank.go
  - exchanges/okx/okx_business_websocket.go
  - exchanges/kucoin/kucoin_websocket.go
  - gctscript/vm/vm.go
- Updated tests to reflect changes in the crypto functions.
- Renamed several functions for clarity, particularly in the context of order book updates across multiple exchanges.

* refactor: replace assert with require for consistency in test assertions

* refactor: Improve Binance futures candlestick test, standardise orderbook update function names and improve test parallelism

* refactor: Replace require.Len with require.Equal for better output in TestGetFuturesKlineData

exchanges/gemini/gemini.go

@@ -2,6 +2,8 @@ package gemini
 
 import (
 	"context"
+	"encoding/base64"
+	"encoding/hex"
 	"errors"
 	"fmt"
 	"maps"
@@ -428,15 +430,13 @@ func (g *Gemini) SendAuthenticatedHTTPRequest(ctx context.Context, ep exchange.U
 
 		maps.Copy(req, params)
 
-		PayloadJSON, err := json.Marshal(req)
+		payload, err := json.Marshal(req)
 		if err != nil {
 			return nil, err
 		}
 
-		PayloadBase64 := crypto.Base64Encode(PayloadJSON)
-		hmac, err := crypto.GetHMAC(crypto.HashSHA512_384,
-			[]byte(PayloadBase64),
-			[]byte(creds.Secret))
+		payloadB64 := base64.StdEncoding.EncodeToString(payload)
+		hmac, err := crypto.GetHMAC(crypto.HashSHA512_384, []byte(payloadB64), []byte(creds.Secret))
 		if err != nil {
 			return nil, err
 		}
@@ -445,8 +445,8 @@ func (g *Gemini) SendAuthenticatedHTTPRequest(ctx context.Context, ep exchange.U
 		headers["Content-Length"] = "0"
 		headers["Content-Type"] = "text/plain"
 		headers["X-GEMINI-APIKEY"] = creds.Key
-		headers["X-GEMINI-PAYLOAD"] = PayloadBase64
-		headers["X-GEMINI-SIGNATURE"] = crypto.HexEncodeToString(hmac)
+		headers["X-GEMINI-PAYLOAD"] = payloadB64
+		headers["X-GEMINI-SIGNATURE"] = hex.EncodeToString(hmac)
 		headers["Cache-Control"] = "no-cache"
 
 		return &request.Item{

exchanges/gemini/gemini_websocket.go

@@ -4,6 +4,8 @@ package gemini
 
 import (
 	"context"
+	"encoding/base64"
+	"encoding/hex"
 	"errors"
 	"fmt"
 	"net/http"
@@ -140,7 +142,7 @@ func (g *Gemini) WsAuth(ctx context.Context, dialer *gws.Dialer) error {
 		Request: "/v1/" + geminiWsOrderEvents,
 		Nonce:   time.Now().UnixNano(),
 	}
-	PayloadJSON, err := json.Marshal(payload)
+	payloadJSON, err := json.Marshal(payload)
 	if err != nil {
 		return fmt.Errorf("%v sendAuthenticatedHTTPRequest: Unable to JSON request", g.Name)
 	}
@@ -149,10 +151,8 @@ func (g *Gemini) WsAuth(ctx context.Context, dialer *gws.Dialer) error {
 		return err
 	}
 	endpoint := wsEndpoint + geminiWsOrderEvents
-	PayloadBase64 := crypto.Base64Encode(PayloadJSON)
-	hmac, err := crypto.GetHMAC(crypto.HashSHA512_384,
-		[]byte(PayloadBase64),
-		[]byte(creds.Secret))
+	payloadB64 := base64.StdEncoding.EncodeToString(payloadJSON)
+	hmac, err := crypto.GetHMAC(crypto.HashSHA512_384, []byte(payloadB64), []byte(creds.Secret))
 	if err != nil {
 		return err
 	}
@@ -160,9 +160,9 @@ func (g *Gemini) WsAuth(ctx context.Context, dialer *gws.Dialer) error {
 	headers := http.Header{}
 	headers.Add("Content-Length", "0")
 	headers.Add("Content-Type", "text/plain")
-	headers.Add("X-GEMINI-PAYLOAD", PayloadBase64)
+	headers.Add("X-GEMINI-PAYLOAD", payloadB64)
 	headers.Add("X-GEMINI-APIKEY", creds.Key)
-	headers.Add("X-GEMINI-SIGNATURE", crypto.HexEncodeToString(hmac))
+	headers.Add("X-GEMINI-SIGNATURE", hex.EncodeToString(hmac))
 	headers.Add("Cache-Control", "no-cache")
 
 	err = g.Websocket.AuthConn.Dial(dialer, headers)