Missing users on auto-completion for private projects shared with multiple groups

Summary

Inside each project, users don't have full visibility of all members outside their group. This manifests on the @ mention auto-complete UI.

Steps to reproduce

• Create a private project

• Share it with two different groups. Say:

  • Group 1
  • Group 2

  Users on Group 1 and Group 2 do not overlap

What is the current bug behavior?

Users on "Group 1" can auto-complete users on their group, but not on "Group 2", even though they can see their contributions, and mention them as usual. The API doesn't seem to know this so they do not appear on the autocomplete for @.

What is the expected correct behavior?

User should be able to @ auto-complete every user attached to the current project, even on different groups.

Results of GitLab environment info

This is on present on %13.3