support set gravatar as user avatar provider

pkg/utils/strings.go

@@ -7,6 +7,7 @@ import (
 	"crypto/rand"
 	"crypto/sha256"
 	"encoding/base64"
+	"encoding/hex"
 	"strings"
 	"unicode"
 
@@ -133,6 +134,12 @@ func MD5Encode(data []byte) []byte {
 	return m.Sum(nil)
 }
 
+// MD5EncodeToString returns a hashed string by md5
+func MD5EncodeToString(data []byte) string {
+	hash := MD5Encode(data)
+	return hex.EncodeToString(hash)
+}
+
 // AESGCMEncrypt returns a encrypted string by aes-gcm
 func AESGCMEncrypt(key []byte, plainText []byte) ([]byte, error) {
 	block, err := aes.NewCipher(key)