Auth: Signing Key persistence (#75487)

* signing key wip

use db keyset storage

add signing_key table

add testing for key storage

add ES256 key tests

Remove caching and implement UpdateOrCreate

Stabilize interfaces

* Encrypt private keys

* Fixup signer

* Fixup ext_jwt

* Add GetOrCreatePrivate with automatic key rotation

* use GetOrCreate for ext_jwt

* use GetOrCreate in id

* catch invalid block type

* fix broken test

* remove key generator

* reduce public interface of signing service

pkg/services/sqlstore/migrations/migrations.go

@@ -5,6 +5,7 @@ import (
 	"github.com/grafana/grafana/pkg/services/sqlstore/migrations/accesscontrol"
 	"github.com/grafana/grafana/pkg/services/sqlstore/migrations/anonservice"
 	"github.com/grafana/grafana/pkg/services/sqlstore/migrations/oauthserver"
+	"github.com/grafana/grafana/pkg/services/sqlstore/migrations/signingkeys"
 	"github.com/grafana/grafana/pkg/services/sqlstore/migrations/ualert"
 	. "github.com/grafana/grafana/pkg/services/sqlstore/migrator"
 )
@@ -99,6 +100,7 @@ func (*OSSMigrations) AddMigration(mg *Migrator) {
 	}
 
 	anonservice.AddMigration(mg)
+	signingkeys.AddMigration(mg)
 }
 
 func addStarMigrations(mg *Migrator) {