Provide User Scope in Search API

Problem to solve

Please provide 'user scope'/'user search' in Search API

Further details

With user search, we can do:

• https://gitlab.example.com/api/v4/search?scope=users&search=john
• https://gitlab.example.com/api/v4/search?scope=users&search=john+followers:400

It will have the ability the ability to accept 'where' arguments

eg:

Give me all users 'where' user.followers > 400 and user.contribution > 1000

With 'where' argument support, we can narrow our result and not fetching all users which will take tremendous time. 'user search' in Search API also help us a lot by giving the result of users matching our criteria without doing all tricky things.

For user.follower we have to wait https://gitlab.com/gitlab-org/gitlab-ce/issues/30868 implemented, and for user.contribution we have to wait https://gitlab.com/gitlab-org/gitlab-ce/issues/54730

Proposal

Please provide 'user search' in Search API

What does success look like, and how can we measure that?

We can query search API by user scope and 'where' support.