core&ui: add new features about domain (#528)

Co-authored-by: undefined <i@undefined.moe>

- Add navigation hint
- Update homework/contest filter by assign
- Allow empty query for DomainSelectAutoComplete

packages/hydrooj/src/service/layers/user.ts

@@ -1,5 +1,4 @@
 import { NotFoundError } from '../../error';
-import avatar from '../../lib/avatar';
 import { PERM } from '../../model/builtin';
 import UserModel from '../../model/user';
 import type { KoaContext } from '../server';
@@ -15,7 +14,6 @@ export default async (ctx: KoaContext, next) => {
         user = await UserModel.getById(domainId, ctx.session.uid, ctx.session.scope);
     }
     if (user._id === 0) delete user.viewLang;
-    user.avatarUrl = avatar(user.avatar, 128);
     ctx.HydroContext.user = await user.private();
     if (!domain) {
         ctx.pendingError = new NotFoundError(args.domainId);