Use Repo.get_by(schema, id: id, organization_id: organization_id) instead of
Repo.get + pattern match so that resources from wrong orgs return :not_found
instead of :forbidden, preventing org membership discovery.
- REST CRUD at /api/v1/checks for HTTP, TCP, DNS, ping checks
- GraphQL queries (checks, check) and mutations (create/update/delete)
- ping executor using system ping with macOS/Linux parsing
- check config validation for ping type (requires host)
- API documentation updated with checks resource section
Reviewed-on: graham/towerops-web#52
