[DT-2824] Feature flags

[fboulnois]

Addresses

Summary

Adds feature flags to Consent. The API is:

• GET /api/feature - List all feature flags (unauthenticated)
• GET /api/feature/id - Get a specific flag (unauthenticated)
• POST /api/feature/id - Create/update value (admin-only), body: {"value": "..."}
• DELETE /api/feature/id - Delete a feature flag (admin-only)

Some helper methods exist that consent itself can use to determine if a feature flag is enabled. I kept the value as a string, as we may want multiple states beyond enabled or disabled.

Unit tests cover all functionality.

---

Have you read CONTRIBUTING.md lately? If not, do that first.

• Label PR with a Jira ticket number and include a link to the ticket
• Label PR with a security risk modifier [no, low, medium, high]
• PR describes scope of changes
• Get a minimum of one thumbs worth of review, preferably two if enough team members are available
• Get PO sign-off for all non-trivial UI or workflow changes
• Verify all tests go green
• Test this change deployed correctly and works on dev environment after deployment

[rushtong]

Nice work, thank you 👍🏽

[otchet-broad]

Looks god!
One small item: I think we might want to add some audit logging for adding/removing feature flags so we can track who turned them on or off in a specific environment.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
90.4% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud