feat: implement sign in with idp

internal/util/util.go

@@ -1,6 +1,9 @@
 package util
 
 import (
+	"crypto/rand"
+	"math/big"
+	"net/mail"
 	"strconv"
 	"strings"
 )
@@ -23,3 +26,32 @@ func HasPrefixes(src string, prefixes ...string) bool {
 	}
 	return false
 }
+
+// ValidateEmail validates the email.
+func ValidateEmail(email string) bool {
+	if _, err := mail.ParseAddress(email); err != nil {
+		return false
+	}
+	return true
+}
+
+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
+}