Revert "remove sugar/certificates.go"

This reverts commit a443c9d.

Author: asmyasnikov

sugar/certificates.go

@@ -0,0 +1,44 @@
+package sugar
+
+import (
+	"crypto/x509"
+	"encoding/pem"
+	"io/ioutil"
+	"path/filepath"
+
+	"github.com/ydb-platform/ydb-go-sdk/v3/internal/xerrors"
+)
+
+// LoadCertificatesFromFile read and parse caFile and returns certificates
+func LoadCertificatesFromFile(caFile string) ([]*x509.Certificate, error) {
+	bytes, err := ioutil.ReadFile(filepath.Clean(caFile))
+	if err != nil {
+		return nil, xerrors.WithStackTrace(err)
+	}
+	return LoadCertificatesFromPem(bytes), nil
+}
+
+// LoadCertificatesFromPem parse bytes and returns certificates
+func LoadCertificatesFromPem(bytes []byte) (certs []*x509.Certificate) {
+	var (
+		cert *x509.Certificate
+		err  error
+	)
+	for len(bytes) > 0 {
+		var block *pem.Block
+		block, bytes = pem.Decode(bytes)
+		if block == nil {
+			break
+		}
+		if block.Type != "CERTIFICATE" || len(block.Headers) != 0 {
+			continue
+		}
+		certBytes := block.Bytes
+		cert, err = x509.ParseCertificate(certBytes)
+		if err != nil {
+			continue
+		}
+		certs = append(certs, cert)
+	}
+	return
+}