core: allow lock topic

packages/hydrooj/src/error.ts

@@ -98,6 +98,7 @@ export const DomainJoinForbiddenError = Err('DomainJoinForbiddenError', Forbidde
 export const DomainJoinAlreadyMemberError = Err('DomainJoinAlreadyMemberError', ForbiddenError, 'Failed to join the domain. You are already a member.');
 export const InvalidJoinInvitationCodeError = Err('InvalidJoinInvitationCodeError', ForbiddenError, 'The invitation code you provided is invalid.');
 export const CurrentPasswordError = Err('CurrentPasswordError', ForbiddenError, "Current password doesn't match.");
+export const DiscussionLockedError = Err('DiscussionLockedError', ForbiddenError, 'The discussion is locked, you can not reply anymore.');
 
 export const UserNotFoundError = Err('UserNotFoundError', NotFoundError, 'User {0} not found.');
 export const NoProblemError = Err('NoProblemError', NotFoundError, 'No problem.');