DefaultUserService.swift

func refreshToken(request: Request, refreshTokenDto: RefreshTokenDto) throws -> Future<AccessDto> {
        let refreshTokenModel = RefreshToken
            .query(on: request)
            .filter(\.token == refreshTokenDto.refreshToken)
            .first()
            .unwrap(or: Abort(.unauthorized))
        
        return refreshTokenModel.flatMap { refreshTokenModel in
            if refreshTokenModel.expiredAt > Date() {
                return refreshTokenModel.user.get(on: request).flatMap { user in
                    let accessToken = try TokenHelpers.createAccessToken(from: user)
                    let refreshToken = TokenHelpers.createRefreshToken()
                    let expiredAt = try TokenHelpers.expiredDate(of: accessToken)
                    
                    refreshTokenModel.token = refreshToken
                    refreshTokenModel.updateExpiredDate()
                    
                    let accessDto = AccessDto(refreshToken: refreshToken, accessToken: accessToken, expiredAt: expiredAt)
                    
                    return refreshTokenModel.save(on: request).transform(to: accessDto)
                }
            } else {
                return refreshTokenModel.delete(on: request).thenThrowing {
                    throw Abort(.unauthorized)
                }
            }
      }
}