code: @RequestMapping(path = "", method = RequestMethod.POST)
      public ResponseEntity<Customer> createCustomer(@RequestBody Customer customer){
          Customer newCustomer = customerService.createCustomer(customer);
          if(newCustomer != null){
              return new ResponseEntity<Customer>(newCustomer, HttpStatus.CREATED);
          }else{
              return new ResponseEntity<Customer>(HttpStatus.CONFLICT);
          }
      }
docs: Create new customer
  @param customer new customer
  @response 201 customer is created
  @response 409 customer with the same email already exists
  @return CREATED customer with a customerId or CONFLICT if customer with the same email already exists