Organization visibility setting

In Cells 1.0 an Organization could be public or private. All new organizations will be private and it won't be possible to adjust that setting until a later Cells release. The default organization will remain public.

At the minimum we need a database/model level feature for visibility, and the correct setting per organization. The frontend work might be avoidable for now.

Plan

• Add new column small integer visibility_level to organizations table - !145606 (merged)
• Make the column default to private(0) - !145606 (merged)
• In a post deployment migration, make the default organization(id of 1) to be public(20) - !145606 (merged)
• Add include Gitlab::VisibilityLevel to Organizations::Organization - !145606 (merged)
• Add to default organization seeder - !145606 (merged)
• In a follow-up add logic to Organizations::OrganizationPolicy to change condition(:public_organization, scope: :subject, score: 0) { true } to condition(:public_organization, scope: :subject, score: 0) { @subject.public? }. I still think the score here could be 0 as the organization is already loaded at the time. - !145949 (merged)