refactor: optimize the exception information (#3747)

#### What type of PR is this?
/kind improvement
/area core

#### What this PR does / why we need it:
优化异常信息
- 5xx 服务器内部错误不显示异常详情到页面，如主题模板表达式错误
- 访问 `GET /apis/api.halo.run/v1alpha1/comments` 提示 400 且不会打印异常堆栈
- 访问不存在的主题静态资源提示 404 且不会打印异常堆栈，如 `GET /themes/guqing-higan/assets/dist/style1.css`

#### Which issue(s) this PR fixes:
Fixes #3483

#### Does this PR introduce a user-facing change?
```release-note
None
```

application/src/main/java/run/halo/app/infra/exception/handlers/ProblemDetailErrorAttributes.java

@@ -8,6 +8,7 @@ import java.time.Instant;
 import java.util.LinkedHashMap;
 import java.util.Locale;
 import java.util.Map;
+import java.util.Optional;
 import org.springframework.boot.web.error.ErrorAttributeOptions;
 import org.springframework.boot.web.reactive.error.DefaultErrorAttributes;
 import org.springframework.boot.web.reactive.error.ErrorAttributes;
@@ -39,7 +40,7 @@ public class ProblemDetailErrorAttributes implements ErrorAttributes {
     @Override
     public Map<String, Object> getErrorAttributes(ServerRequest request,
         ErrorAttributeOptions options) {
-        var errAttributes = new LinkedHashMap<String, Object>();
+        final var errAttributes = new LinkedHashMap<String, Object>();
 
         var error = getError(request);
         var responseStatusAnno = from(error.getClass(), SearchStrategy.TYPE_HIERARCHY)
@@ -50,8 +51,12 @@ public class ProblemDetailErrorAttributes implements ErrorAttributes {
         if (error instanceof ErrorResponse er) {
             errorResponse = er;
         } else {
-            var reason = responseStatusAnno.getValue("reason", String.class)
+            var reason = Optional.of(status)
-                .orElse(error.getMessage());
+                .filter(HttpStatusCode::is5xxServerError)
+                .map(s -> "Something went wrong, please try again later.")
+                .orElseGet(() -> responseStatusAnno.getValue("reason", String.class)
+                    .orElse(error.getMessage())
+                );
             errorResponse = ErrorResponse.create(error, status, reason);
         }
         var problemDetail =

application/src/main/java/run/halo/app/theme/ThemeConfiguration.java

@@ -46,6 +46,9 @@ public class ThemeConfiguration {
                 var resource = request.pathVariable("resource");
                 resource = StringUtils.removeStart(resource, "/");
                 var fsRes = new FileSystemResource(getThemeAssetsPath(themeName, resource));
+                if (!fsRes.exists()) {
+                    return ServerResponse.notFound().build();
+                }
                 var bodyBuilder = ServerResponse.ok()
                     .cacheControl(cacheProperties.getCachecontrol().toHttpCacheControl());
                 try {

application/src/main/java/run/halo/app/theme/endpoint/CommentFinderEndpoint.java

@@ -22,6 +22,7 @@ import org.springframework.util.MultiValueMap;
 import org.springframework.web.reactive.function.server.RouterFunction;
 import org.springframework.web.reactive.function.server.ServerRequest;
 import org.springframework.web.reactive.function.server.ServerResponse;
+import org.springframework.web.server.ServerWebInputException;
 import reactor.core.publisher.Mono;
 import reactor.core.scheduler.Schedulers;
 import run.halo.app.content.comment.CommentRequest;
@@ -230,7 +231,7 @@ public class CommentFinderEndpoint implements CustomEndpoint {
         public String getKind() {
             String kind = emptyToNull(queryParams.getFirst("kind"));
             if (kind == null) {
-                throw new IllegalArgumentException("The kind must not be null.");
+                throw new ServerWebInputException("The kind must not be null.");
             }
             return kind;
         }
@@ -244,7 +245,7 @@ public class CommentFinderEndpoint implements CustomEndpoint {
         public String getName() {
             String name = emptyToNull(queryParams.getFirst("name"));
             if (name == null) {
-                throw new IllegalArgumentException("The name must not be null.");
+                throw new ServerWebInputException("The name must not be null.");
             }
             return name;
         }

application/src/test/java/run/halo/app/infra/exception/handlers/I18nExceptionTest.java

@@ -105,13 +105,14 @@ class I18nExceptionTest {
 
     @Test
     void shouldGetErrorIfThrowingGeneralException() {
+        // problem reason will be a fixed prompt when internal server error occurred.
         webClient.get().uri("/response-entity/general-error")
             .exchange()
             .expectStatus().isEqualTo(HttpStatus.INTERNAL_SERVER_ERROR)
             .expectBody(ProblemDetail.class)
             .value(problemDetail -> {
                 assertEquals("Internal Server Error", problemDetail.getTitle());
-                assertEquals("Something went wrong",
+                assertEquals("Something went wrong, please try again later.",
                     problemDetail.getDetail());
             });
     }