class JwtTokenUtil {

    public String generateRefreshToken(String subject) {
    	final Instant createdDate = Instant.now();
    	final Instant expirationDate = createdDate.plus(jwtConfig.getRefreshExpiration());
    	
    	log.info("generateRefreshToken()");
        
        return Jwts.builder()
        		.setSubject(subject)
                .setIssuedAt(Date.from(createdDate))
                .setExpiration(Date.from(expirationDate))
                .signWith(Keys.hmacShaKeyFor(Decoders.BASE64.decode(jwtConfig.getSecret())), SignatureAlgorithm.HS512)
                .compact();
    }

}