add basic user authentication

internal/jwtauth/jwt.go

@@ -0,0 +1,22 @@
+package jwtauth
+
+import (
+	"encoding/base64"
+	"os"
+
+	"github.com/golang-jwt/jwt/v5"
+)
+
+func GenerateJwtToken(username string) (string, error) {
+	var s string
+	key, err := base64.URLEncoding.DecodeString(os.Getenv(getKeyVariableName()))
+	if err != nil {
+		return s, err
+	}
+	t := jwt.NewWithClaims(jwt.SigningMethodHS256,
+		jwt.MapClaims{
+			"iss": "PersonalLibraryManager",
+			"sub": username,
+		})
+	return t.SignedString(key)
+}