private bool IsDoctorAvailable(string doctorJmbg, DateTime dateTime)
        {
            if (!_doctorRepository.CheckIfDoctorExists(doctorJmbg))
            {
                throw new BadRequestException("Doctor doesn't exist in database.");
            }

            if (_examinationRepository.GetExaminationsByDoctorAndDateTime(doctorJmbg, dateTime).Count > 0)
            {
                return(false);
            }

            return(true);
        }