The `members` table can have entries where `user_id: nil`, because people can
invite group members by email. We never want to include those as members,
because it might cause confusion with the anonymous (logged out) user.

Allow to access pipelines even if they are disabled, but only present jobs and commit statuses without giving ability to access them

Signed-off-by: NRémy Coutable <remy@rymai.me>

Some changes in EE for the auditor user feature need
to be backported to CE to avoid merge conflicts. This
commit encapsulates all these backports.

- The pages are created when build artifacts for `pages` job are uploaded
- Pages serve the content under: http://group.pages.domain.com/project
- Pages can be used to serve the group page, special project named as host: group.pages.domain.com
- User can provide own 403 and 404 error pages by creating 403.html and 404.html in group page project
- Pages can be explicitly removed from the project by clicking Remove Pages in Project Settings
- The size of pages is limited by Application Setting: max pages size, which limits the maximum size of unpacked archive (default: 100MB)
- The public/ is extracted from artifacts and content is served as static pages
- Pages asynchronous worker use `dd` to limit the unpacked tar size
- Pages needs to be explicitly enabled and domain needs to be specified in gitlab.yml
- Pages are part of backups
- Pages notify the deployment status using Commit Status API
- Pages use a new sidekiq queue: pages
- Pages use a separate nginx config which needs to be explicitly added

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Fixes #18448

Due to different way of handling owners of a project, they were not allowed to fetch CI sources for project.

- Public projects - anyone can access
- Private projects - any member (guest level and above) can access

Use a permissions of user to access all dependent projects from CI jobs (this also includes a container images, and in future LFS files)