core: better user_file permission control

packages/hydrooj/src/handler/problem.ts

@@ -11,8 +11,8 @@ import {
     ValidationError,
 } from '../error';
 import {
-    ProblemConfig, ProblemDoc, ProblemStatusDoc,
-    Tdoc, User,
+    ProblemDoc, ProblemStatusDoc, Tdoc,
+    User,
 } from '../interface';
 import paginate from '../lib/paginate';
 import { isPid, parsePid as convertPid } from '../lib/validator';