Unable to search for issues assigned to numerical usernames
Summary
After upgrade to version 14.10, the users are unable to filter issues assigned to users that have numerical usernames (e.g: @123456789).
Steps to reproduce
Assign an issue to a user with numerical username.
Example Project
I've created a project with a issue assigned to a user (that I don't know) with username @123456789.
What is the current bug behavior?
The issue list is empty OR can show wrong results (e.g.: if I search for the username @123, the result will be filtered by the "userId: 123")
What is the expected correct behavior?
A list with issues assigned to username 123456789
Relevant logs and/or screenshots
Output of checks
This bug happens on GitLab.com
Possible fixes
The problem can be here: https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/assets/javascripts/issues/list/utils.js#L207
While using dashboard search, the problem doesn't happens: https://gitlab.com/dashboard/issues?scope=all&state=opened&assignee_username=123456789
/cc @cngo