User is not shown in autocomplete window when inviting member to group

Summary

Cannot invite Alexand to group.

User is not shown in autocomplete window, even though we enter exact username. Partially matching usernames are shown.

Steps to reproduce

1. Go to the group's Member page
2. Enter @Alexand
3. A list of Alexanders show on the auto complete. I cannot invite @Alexand to the group as he is not appearing.
4. To add insult to injury, the textbox is then cleared out. :(

Screen_Recording_2020-04-23_at_9.07.50_PM

Example Project

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What is the current bug behavior?

A list of less exact matches appear first. In fact the exact match never appears

What is the expected correct behavior?

The exact matched username should appear first

Relevant logs and/or screenshots

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Output of checks

This bug happens on GitLab.com

Results of GitLab environment info

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Results of GitLab application Check

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sudo gitlab-rake gitlab:check SANITIZE=true)
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sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)
(we will only investigate if the tests are passing)

Possible fixes

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Workaround

Ask for the user's email address instead