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

common/crypto/crypto.go

@@ -7,8 +7,6 @@ import (
 	"crypto/sha1" //nolint:gosec // Used for exchanges
 	"crypto/sha256"
 	"crypto/sha512"
-	"encoding/base64"
-	"encoding/hex"
 	"errors"
 	"hash"
 	"io"
@@ -23,25 +21,6 @@ const (
 	HashMD5
 )
 
-// HexEncodeToString takes in a hexadecimal byte array and returns a string
-func HexEncodeToString(input []byte) string {
-	return hex.EncodeToString(input)
-}
-
-// Base64Decode takes in a Base64 string and returns a byte array and an error
-func Base64Decode(input string) ([]byte, error) {
-	result, err := base64.StdEncoding.DecodeString(input)
-	if err != nil {
-		return nil, err
-	}
-	return result, nil
-}
-
-// Base64Encode takes in a byte array then returns an encoded base64 string
-func Base64Encode(input []byte) string {
-	return base64.StdEncoding.EncodeToString(input)
-}
-
 // GetRandomSalt returns a random salt
 func GetRandomSalt(input []byte, saltLen int) ([]byte, error) {
 	if saltLen <= 0 {
@@ -60,27 +39,6 @@ func GetRandomSalt(input []byte, saltLen int) ([]byte, error) {
 	return result, nil
 }
 
-// GetMD5 returns a MD5 hash of a byte array
-func GetMD5(input []byte) ([]byte, error) {
-	m := md5.New() //nolint:gosec // hash function used by some exchanges
-	_, err := m.Write(input)
-	return m.Sum(nil), err
-}
-
-// GetSHA512 returns a SHA512 hash of a byte array
-func GetSHA512(input []byte) ([]byte, error) {
-	sha := sha512.New()
-	_, err := sha.Write(input)
-	return sha.Sum(nil), err
-}
-
-// GetSHA256 returns a SHA256 hash of a byte array
-func GetSHA256(input []byte) ([]byte, error) {
-	sha := sha256.New()
-	_, err := sha.Write(input)
-	return sha.Sum(nil), err
-}
-
 // GetHMAC returns a keyed-hash message authentication code using the desired
 // hashtype
 func GetHMAC(hashType int, input, key []byte) ([]byte, error) {

common/crypto/crypto_test.go

@@ -2,36 +2,12 @@ package crypto
 
 import (
 	"bytes"
-	"encoding/hex"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
-func TestHexEncodeToString(t *testing.T) {
-	t.Parallel()
-	assert.Equal(t, "737472696e67", HexEncodeToString([]byte("string")))
-}
-
-func TestBase64Decode(t *testing.T) {
-	t.Parallel()
-
-	r, err := Base64Decode("aGVsbG8=")
-	require.NoError(t, err, "Base64Decode must not error")
-	assert.Equal(t, []byte("hello"), r, "Base64Decode should return the correct byte slice")
-
-	_, err = Base64Decode("-")
-	assert.Error(t, err, "Base64Decode should error on invalid input")
-}
-
-func TestBase64Encode(t *testing.T) {
-	t.Parallel()
-
-	assert.Equal(t, "aGVsbG8=", Base64Encode([]byte("hello")),
-		"Base64Encode should return the correct base64 string")
-}
-
 func TestGetRandomSalt(t *testing.T) {
 	t.Parallel()
 
@@ -47,48 +23,6 @@ func TestGetRandomSalt(t *testing.T) {
 	assert.Len(t, salt, 16, "GetRandomSalt should return a salt of the specified length plus input length")
 }
 
-func TestGetMD5(t *testing.T) {
-	t.Parallel()
-	r, err := GetMD5([]byte("I am testing the MD5 function in common!"))
-	require.NoError(t, err, "GetMD5 must not error")
-	assert.Equal(t, "18fddf4a41ba90a7352765e62e7a8744", hex.EncodeToString(r), "GetMD5 result should match the expected output")
-}
-
-func TestGetSHA512(t *testing.T) {
-	t.Parallel()
-	originalString := []byte("I am testing the GetSHA512 function in common!")
-	expectedOutput := []byte(
-		`a2273f492ea73fddc4f25c267b34b3b74998bd8a6301149e1e1c835678e3c0b90859fce22e4e7af33bde1711cbb924809aedf5d759d648d61774b7185c5dc02b`,
-	)
-	actualOutput, err := GetSHA512(originalString)
-	if err != nil {
-		t.Fatal(err)
-	}
-	actualStr := HexEncodeToString(actualOutput)
-	if !bytes.Equal(expectedOutput, []byte(actualStr)) {
-		t.Errorf("Expected '%x'. Actual '%x'",
-			expectedOutput, []byte(actualStr))
-	}
-}
-
-func TestGetSHA256(t *testing.T) {
-	t.Parallel()
-	originalString := []byte("I am testing the GetSHA256 function in common!")
-	expectedOutput := []byte(
-		"0962813d7a9f739cdcb7f0c0be0c2a13bd630167e6e54468266e4af6b1ad9303",
-	)
-	actualOutput, err := GetSHA256(originalString)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	actualStr := HexEncodeToString(actualOutput)
-	if !bytes.Equal(expectedOutput, []byte(actualStr)) {
-		t.Errorf("Expected '%x'. Actual '%x'", expectedOutput,
-			[]byte(actualStr))
-	}
-}
-
 func TestGetHMAC(t *testing.T) {
 	t.Parallel()
 	expectedSha1 := []byte{