remove bson & pandora support

hydro/handler/contest.js

@@ -1,5 +1,5 @@
 const moment = require('moment-timezone');
-const { ObjectID } = require('bson');
+const { ObjectID } = require('mongodb');
 const AdmZip = require('adm-zip');
 const {
     ContestNotLiveError, ValidationError, ProblemNotFoundError,

hydro/handler/discussion.js

@@ -1,4 +1,4 @@
-const { ObjectID } = require('bson');
+const { ObjectID } = require('mongodb');
 const paginate = require('../lib/paginate');
 const system = require('../model/system');
 const user = require('../model/user');

hydro/handler/homework.js

@@ -1,6 +1,6 @@
 const yaml = require('js-yaml');
 const moment = require('moment-timezone');
-const { ObjectID } = require('bson');
+const { ObjectID } = require('mongodb');
 const AdmZip = require('adm-zip');
 const {
     ValidationError, HomeworkNotLiveError, ProblemNotFoundError,

hydro/handler/record.js

@@ -1,4 +1,4 @@
-const { ObjectID } = require('bson');
+const { ObjectID } = require('mongodb');
 const { PermissionError } = require('../error');
 const { PERM_READ_RECORD_CODE, PERM_REJUDGE, PERM_VIEW_PROBLEM_HIDDEN } = require('../model/builtin').PERM;
 const problem = require('../model/problem');