feat: implement sign in with SSO (#1119)

* feat: implement sign in with SSO

* chore: update

* chore: update

* chore: update

common/util.go

@@ -1,6 +1,8 @@
 package common
 
 import (
+	"crypto/rand"
+	"math/big"
 	"net/mail"
 	"strings"
 
@@ -35,3 +37,24 @@ func Min(x, y int) int {
 	}
 	return y
 }
+
+var letters = []rune("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
+
+// RandomString returns a random string with length n.
+func RandomString(n int) (string, error) {
+	var sb strings.Builder
+	sb.Grow(n)
+	for i := 0; i < n; i++ {
+		// The reason for using crypto/rand instead of math/rand is that
+		// the former relies on hardware to generate random numbers and
+		// thus has a stronger source of random numbers.
+		randNum, err := rand.Int(rand.Reader, big.NewInt(int64(len(letters))))
+		if err != nil {
+			return "", err
+		}
+		if _, err := sb.WriteRune(letters[randNum.Uint64()]); err != nil {
+			return "", err
+		}
+	}
+	return sb.String(), nil
+}