fix(mapper): correct BorrowRecordMapper entity type and add unauthorized helper

- Fix import and generic type from Book to BorrowRecord in mapper
- Add unauthorized helper returning 401 status to Result template

src/main/kotlin/com/msksbr/bookmgr/mapper/BorrowRecordMapper.kt

@@ -1,8 +1,8 @@
 package com.msksbr.bookmgr.mapper
 
 import com.baomidou.mybatisplus.core.mapper.BaseMapper
-import com.msksbr.bookmgr.entity.Book
+import com.msksbr.bookmgr.entity.BorrowRecord
 import org.apache.ibatis.annotations.Mapper
 
 @Mapper
-interface BorrowRecordMapper: BaseMapper<Book>
+interface BorrowRecordMapper: BaseMapper<BorrowRecord>

src/main/kotlin/com/msksbr/bookmgr/template/Result.kt

@@ -22,5 +22,13 @@ data class Result<T>(
                 data = null
             )
         }
+        // 未登录
+        fun <T> unauthorized(message: String): Result<T> {
+            return Result(
+                code = 401,
+                message = message,
+                data = null
+            )
+        }
     }
 }