pluggable secret backend

This commit extends SwarmKit secret management with pluggable secret
backends support.

Updating the work in
[swarmkit](docker/swarmkit@eebac27434) for
pluggable secret backend and adding the
driver parameter to `SecretSpec`.

Remaining work:
- [ ] CLI support (docker/cli)
- [ ] api in [plugin helpers](docker/go-plugins-helpers))
- [ ] Reference plugin
- [ ] Documenation (after cli work)

Signed-off-by: Liron Levin <liron@twistlock.com>
Upstream-commit: 7d45cafd5746e847e58078aa2fbdde57b5f49fa4
Component: engine

components/engine/daemon/cluster/convert/secret.go

@@ -13,6 +13,7 @@ func SecretFromGRPC(s *swarmapi.Secret) swarmtypes.Secret {
 		Spec: swarmtypes.SecretSpec{
 			Annotations: annotationsFromGRPC(s.Spec.Annotations),
 			Data:        s.Spec.Data,
+			Driver:      driverFromGRPC(s.Spec.Driver),
 		},
 	}
 
@@ -31,7 +32,8 @@ func SecretSpecToGRPC(s swarmtypes.SecretSpec) swarmapi.SecretSpec {
 			Name:   s.Name,
 			Labels: s.Labels,
 		},
-		Data: s.Data,
+		Data:   s.Data,
+		Driver: driverToGRPC(s.Driver),
 	}
 }