fix: 修改了preUploadFile接口的返回

src/main/kotlin/cn/edu/hfut/auto/knowledge/controller/KnowledgeController.kt

@@ -35,7 +35,7 @@ class KnowledgeController(
     @SaCheckRole("1")
     @Transactional(rollbackFor = [Throwable::class])
     @PostMapping("/file")
-    suspend fun preUploadFile(@RequestBody vo: KnowledgeFileUploadVO): String {
+    suspend fun preUploadFile(@RequestBody vo: KnowledgeFileUploadVO): FileTicket {
         knowledgeRepository.findByNameAndParentId(vo.name, vo.parentId, Knowledge.AS_CHILD_FETCHER)?.let {
             throw BusinessError(ErrorCode.TARGET_ALREADY_EXISTS)
         }
@@ -65,7 +65,7 @@ class KnowledgeController(
             } catch (e: KafkaException) {
                 throw BusinessError(ErrorCode.MESSAGING_FAILED, cause = e)
             }
-            return ticket
+            return this
         }
     }
 }