code: public String signToken(AuthenticatedUser user) {
          Date expiry = new Date(System.currentTimeMillis() + this.jwtTimeout);
          JWTClaimsSet claimsSet = user.toClaimSet(this.jwtIssuer, expiry);
          SignedJWT jwt = this.signToken(claimsSet);
          return jwt.serialize();
      }
docs: Sign the given claims
  
  @param user the user to create the claims from
  @return the created and signed JSON Web Token as string