Fix private comment Elasticsearch leak

See merge request gitlab/gitlabhq!3521

Hide AWS secret on Admin Integration page

See merge request gitlab/gitlabhq!3525

Related Branches Visible to Guests in Issue Activity

See merge request gitlab/gitlabhq!3537

Fix invalid byte sequence

See merge request gitlab/gitlabhq!3545

Check permissions before showing a forked project's source

See merge request gitlab/gitlabhq!3554

Ensure attributes that end in `_ids` are cleaned

See merge request gitlab/gitlabhq!3561

[ci skip]

This prevents an issue where you can steal other projects objects by
asking for ids that don't belong to you in import.

Disabled features are ignored as they are grey areas

Some feature allows GUEST to access only if project is not private.
This method returns access level when targeting private projects.

Guest are blocked to certain feature when project is private,
therefore the scope would filter additionally with REPORTER level.

Remove impossible cases due to private project's features can only be
private or disabled.

Fix spec due to sidekiq indexing not triggered.

Update guest use cases: some features has additional constraint that
"Guest users are able to perform action on public/internal projects,
but not private ones."

[ci skip]