New storage_backends table is the runtime inventory of pluggable
infrastructure choices (KMS, encrypted_keys, blob, eventbus, cache).
Each kind has exactly one active row, enforced via a partial unique
index. Read-only rows are env-var driven; UI-mutable rows can be
flipped via SetActive.
settings.Registrar reflects boot-time backend choices into the table
so the admin UI sees what's actually running.
New admin endpoints under /admin/settings/backends:
GET /settings/backends?kind=...
GET /settings/backends/active/:kind
POST /settings/backends/:id/activate
New internal endpoints under /api/v1/internal:
GET /worker/config - workers fetch runtime config on boot
POST /worker/heartbeat - liveness ping
(DEK endpoints added in the encryptedkeys commit.)
handler.Handler grows EncryptedKeys + StorageBackendRepo fields.
5 registrar tests cover create / update-and-activate / skip-when-active /
lookup-error propagation / RegisterAll stop-on-first-error using a
mock repository.
Matthew Meszaros