feat(JwtAuthenticationToken): 직렬화 지원 추가

- principal 필드를 직렬화 가능하도록 수정
- credentials 필드는 인증 이후에 사용하지 않으니 직렬화 제외
- 세션 저장 및 분산 서버 환경에서의 호환성 확보

Author: m-a-king

src/main/java/com/somemore/auth/jwt/filter/JwtAuthenticationToken.java

@@ -3,13 +3,14 @@
 import org.springframework.security.authentication.AbstractAuthenticationToken;
 import org.springframework.security.core.GrantedAuthority;
 
+import java.io.Serializable;
 import java.util.Collection;
 
 public class JwtAuthenticationToken extends AbstractAuthenticationToken {
-    private final Object principal;
-    private final Object credentials;
+    private final Serializable principal;
+    private final transient Object credentials;
 
-    public JwtAuthenticationToken(Object principal,
+    public JwtAuthenticationToken(Serializable principal,
                                   Object credentials,
                                   Collection<? extends GrantedAuthority> authorities) {
         super(authorities);