Encryption: Extend secrets service to support registering key providers (#40626)

* Draft adding kms providers

* Rename defaultProvider to currentProvider

* Add getting current provider from config

* Remove comments

* Make current provider service struct field

* Add methods to secrets service

* Test getting current provider

* Implements missing methods for fake secrets service

* Remove accidental changes

* Fix linter issue

* Update configuration examples

* Rename CurrentProvider method

* Split service interface

* Update wire

Co-authored-by: spinillos <selenepinillos@gmail.com>

pkg/services/secrets/manager/manager.go

@@ -36,14 +36,15 @@ func ProvideSecretsService(store secrets.Store, bus bus.Bus, enc encryption.Serv
 	providers := map[string]secrets.Provider{
 		defaultProvider: grafana.New(settings, enc),
 	}
+	currentProvider := settings.KeyValue("security", "encryption_provider").MustString(defaultProvider)
 
 	s := &SecretsService{
 		store:           store,
 		bus:             bus,
 		enc:             enc,
 		settings:        settings,
-		currentProvider: defaultProvider,
 		providers:       providers,
+		currentProvider: currentProvider,
 		dataKeyCache:    make(map[string]dataKeyCacheItem),
 	}
 
@@ -257,3 +258,15 @@ func (s *SecretsService) dataKey(ctx context.Context, name string) ([]byte, erro
 
 	return decrypted, nil
 }
+
+func (s *SecretsService) RegisterProvider(providerID string, provider secrets.Provider) {
+	s.providers[providerID] = provider
+}
+
+func (s *SecretsService) CurrentProviderID() string {
+	return s.currentProvider
+}
+
+func (s *SecretsService) GetProviders() map[string]secrets.Provider {
+	return s.providers
+}