@RequestMapping(value = "/customers/{id}", method = RequestMethod.DELETE)
 ResponseEntity<?> delete(@PathVariable Long id) {
   return this.customerRepository
       .findById(id)
       .map(
           c -> {
             customerRepository.delete(c);
             return ResponseEntity.noContent().build();
           })
       .orElseThrow(() -> new CustomerNotFoundException(id));
 }