Unpublish details for confidential issues

What does this MR do?

Part of #205168 (closed) and #205165 (closed).

Currently, we are making sure not to upload any confidential issues (incidents details and list).

This MR makes sure to unpublish incident details from CDN if an issues become confidential.

Note, this MR is behind a beta feature flag and we tracking the rollout in #210026 (closed) hence also the missing changelog entry.

Screenshots

Making a public 🔓 issue confidential 🔒 removes the incident details (data/incidents/1.json) from the CDN.

Note, that data/list.json does not change as we are already ignoring confidential issues in the list view.

database query plans

⚠ All SQL queries below will be executed in a background job and not during a web request.

Parameters used for these plans:

• project_id: 278964 - https://gitlab.com/gitlab-org/gitlab
• issue_id: 30998761 - #207181 (closed)

StatusPage::IncidentsFinder#find_by_id

Click to expand

Query:

SELECT "issues".*
  FROM "issues"
  WHERE "issues"."project_id" = 278964 AND "issues"."id" = 30998761
LIMIT 1;

Plan: https://explain.depesz.com/s/95DF

Recommendations:

✅ Looks good

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

• [-] Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team