Api : demande absolument un Optional

/**
     * GET  /agences/:id/taux : get tauxes for the "id" agence.
     *
     * @param id the id of the agence to retrieve
     * @return the ResponseEntity with status 200 (OK) and with body tauxes between startDate and endDate, or with status 404 (Not Found)
     */
    @GetMapping("/agences/{id}/taux/{startDate}/{endDate}")
    @Timed
    public ResponseEntity<Agence> getAgenceTaux(@PathVariable Long id, @PathVariable Instant startDate, @PathVariable Instant endDate) {
        log.debug("REST request to get Tauxes for agence : {}", id);
        Optional<Agence> agence = agenceRepository.findById(id);
        Set<Taux>tauxes = agence.get().getTauxes();
        return ResponseUtil.wrapOrNotFound(tauxes);
    }