[FCM] FCM V1 으로 마이그레이션

기존 FCM API deprecated 되어서 v1으로 마이그레이션 함.

  // 데이터 + 메세지
  public int sendMessage(String token, String title, String body, HashMap<String, String> data) throws IOException {
      String message = makeMessage(token, title, body, data);
      return sendMessageToFCM(message);
  }
    
  private String makeMessage(String token, String title, String body, HashMap<String, String> data) throws JsonProcessingException {
        ObjectMapper om = new ObjectMapper();
        FcmMessageDto fcmMessageDto = FcmMessageDto.builder()
                .message(FcmRequestDto.builder()
                        .token(token)
                        .data(data)
                        .notification(FcmRequestDto.Notification.builder()
                                .title(title)
                                .body(body)
                                .build())
                        .build())
                .build();
        return om.writeValueAsString(fcmMessageDto);
    }

    private int sendMessageToFCM(String message) throws IOException {
        RestTemplate restTemplate = new RestTemplate();
        restTemplate.getMessageConverters().add(0, new StringHttpMessageConverter(StandardCharsets.UTF_8));

        String accessToken = getAccessToken();
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_JSON);
        headers.set("Authorization", "Bearer " + accessToken);

        System.out.print("Access Token: " + accessToken);
        HttpEntity<String> entity = new HttpEntity<>(message, headers);

        String API_URL = "https://fcm.googleapis.com/v1/projects/project/messages:send";
        ResponseEntity<String> response = restTemplate.exchange(API_URL, HttpMethod.POST, entity, String.class);

        // 푸시 알림 결과 출력
        System.out.println("Response Status Code: " + response.getStatusCode());
        System.out.println("Response Body: " + response.getBody());

        return response.getStatusCode() == HttpStatus.OK ? 1 : 0;
    }
    
    private String getAccessToken() throws IOException {
        GoogleCredentials googleCredentials = GoogleCredentials
                .fromStream(new ClassPathResource(firebaseKeyPath).getInputStream())
                .createScoped(List.of("https://www.googleapis.com/auth/cloud-platform"));

        googleCredentials.refreshIfExpired();
        return googleCredentials.getAccessToken().getTokenValue();
    }