presto-base-jdbc/src/main/java/io/prestosql/plugin/jdbc/JdbcIdentity.java/JdbcIdentity/toString
class JdbcIdentity:    @Override
    public String toString()
    {
        return toStringHelper(this)
                .add("user", user)
                .add("extraCredentials", extraCredentials.keySet())
                .toString();
    }