♻️ refactor: 매직 스트링 제거

Author: jiwon1217

backend/src/main/java/io/f1/backend/domain/user/app/CustomOAuthUserService.java

@@ -1,5 +1,7 @@
 package io.f1.backend.domain.user.app;
 
+import static io.f1.backend.domain.user.constants.SessionKeys.*;
+
 import io.f1.backend.domain.stat.entity.Stat;
 import io.f1.backend.domain.user.dao.UserRepository;
 import io.f1.backend.domain.user.dto.AuthenticationUser;
@@ -37,7 +39,7 @@ public OAuth2User loadUser(OAuth2UserRequest userRequest) throws OAuth2Authentic
                 .map(this::updateLastLogin)
                 .orElseGet(() -> createNewUser(provider, providerId));
 
-        httpSession.setAttribute("OAuthUser", AuthenticationUser.from(user));
+        httpSession.setAttribute(OAUTH_USER, AuthenticationUser.from(user));
         return new UserPrincipal(user, oAuth2User.getAttributes());
     }
 

backend/src/main/java/io/f1/backend/domain/user/app/UserService.java

@@ -1,5 +1,7 @@
 package io.f1.backend.domain.user.app;
 
+import static io.f1.backend.domain.user.constants.SessionKeys.OAUTH_USER;
+import static io.f1.backend.domain.user.constants.SessionKeys.USER;
 import static io.f1.backend.domain.user.mapper.UserMapper.toSignupResponse;
 
 import io.f1.backend.domain.user.dao.UserRepository;
@@ -36,7 +38,7 @@ public SignupResponseDto signup(HttpSession session, SignupRequestDto signupRequ
 
     private AuthenticationUser extractSessionUser(HttpSession session) {
         AuthenticationUser authenticationUser = (AuthenticationUser) session.getAttribute(
-            "OAuthUser");
+            OAUTH_USER);
         if (authenticationUser == null) {
             throw new RuntimeException("E401001: 로그인이 필요합니다.");
         }
@@ -73,7 +75,7 @@ public User updateUserNickname(Long userId, String nickname) {
     }
 
     private void updateSessionAfterSignup(HttpSession session, User user) {
-        session.removeAttribute("OAuthUser");
-        session.setAttribute("user", AuthenticationUser.from(user));
+        session.removeAttribute(OAUTH_USER);
+        session.setAttribute(USER, AuthenticationUser.from(user));
     }
 }

backend/src/main/java/io/f1/backend/domain/user/constants/SessionKeys.java

@@ -0,0 +1,10 @@
+package io.f1.backend.domain.user.constants;
+
+public final class SessionKeys {
+
+    private SessionKeys() {
+    }
+
+    public static final String OAUTH_USER = "OAuthUser";
+    public static final String USER = "user";
+}