feat(JwtExceptionFilter): JWT 예외 처리 필터 구현

- JWT 처리 중 발생하는 JwtException을 전용 필터에서 처리 (스프링 컨텍스트가 아니므로)
- HTTP 상태 코드 401(Unauthorized)와 함께 ProblemDetail 형식의 JSON 응답 생성
- ProblemDetail 응답에 오류 제목, 유형, 상세 메시지, 타임스탬프 포함

Author: m-a-king

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

@@ -0,0 +1,52 @@
+package com.somemore.auth.jwt.filter;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.somemore.auth.jwt.exception.JwtException;
+import jakarta.servlet.FilterChain;
+import jakarta.servlet.ServletException;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.MediaType;
+import org.springframework.http.ProblemDetail;
+import org.springframework.stereotype.Component;
+import org.springframework.web.filter.OncePerRequestFilter;
+
+import java.io.IOException;
+import java.net.URI;
+
+@RequiredArgsConstructor
+@Slf4j
+@Component
+public class JwtExceptionFilter extends OncePerRequestFilter {
+
+    private final ObjectMapper objectMapper;
+
+    @Override
+    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
+        try {
+            filterChain.doFilter(request, response);
+        } catch (JwtException e) {
+            ProblemDetail problemDetail = buildUnauthorizedProblemDetail(e);
+            configureUnauthorizedResponse(response);
+
+            objectMapper.writeValue(response.getWriter(), problemDetail);
+        }
+    }
+
+    private void configureUnauthorizedResponse(HttpServletResponse response) {
+        response.setStatus(HttpStatus.UNAUTHORIZED.value());
+        response.setContentType(MediaType.APPLICATION_PROBLEM_JSON_VALUE);
+        response.setCharacterEncoding("UTF-8");
+    }
+
+    private ProblemDetail buildUnauthorizedProblemDetail(JwtException e) {
+        ProblemDetail problemDetail = ProblemDetail.forStatusAndDetail(HttpStatus.UNAUTHORIZED, e.getMessage());
+        problemDetail.setTitle("Authentication Error");
+        problemDetail.setType(URI.create("http://프론트엔드주소/errors/unauthorized"));
+        problemDetail.setProperty("timestamp", System.currentTimeMillis());
+        return problemDetail;
+    }
+}