feat: fcm account key 접근 방식 변경(#84)

- 기존에는 'classpath:~' 를 루트로 하는 경로를 이용해 fcm account key를 접근
- 배포시에 해당 경로를 인식하지 못해 리소스를 접근하지 못하는 에러 발생
- spring에서 제공하는 ClassPathResource를 이용하여 접근하는 방식으로 변경

be/src/main/java/yeonba/be/config/FcmConfig.java

@@ -4,26 +4,25 @@
 import com.google.firebase.FirebaseApp;
 import com.google.firebase.FirebaseOptions;
 import com.google.firebase.messaging.FirebaseMessaging;
-import java.io.FileInputStream;
 import java.io.IOException;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
-import org.springframework.core.io.Resource;
+import org.springframework.core.io.ClassPathResource;
 
 @Configuration
 public class FcmConfig {
 
     @Value("${FCM_ACCOUNT_KEY_PATH}")
-    private Resource accountKey;
+    private String fcmAccountKeyPath;
 
     @Bean
     public FirebaseMessaging firebaseMessaging() throws IOException {
 
-        FileInputStream serviceAccount = new FileInputStream(accountKey.getFile());
+        ClassPathResource resource = new ClassPathResource(fcmAccountKeyPath);
 
         FirebaseOptions firebaseOptions = FirebaseOptions.builder()
-            .setCredentials(GoogleCredentials.fromStream(serviceAccount))
+            .setCredentials(GoogleCredentials.fromStream(resource.getInputStream()))
             .build();
 
         return FirebaseMessaging.getInstance(FirebaseApp.initializeApp(firebaseOptions));