Imported members are not shown on project_members page

What does this MR do and why?

Currently, "invited group"(group_project_link) members are not shown on project members page, and I'm not sure if they are shown somewhere else

This makes imported members be shown on project_members page.

This feels like a bug to me, but it might as well be a feature?!

Screenshots or screen recordings

In this case user_d has been 'invited' from group_external.
Before:
After:

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