api: add gRPC definition for version endpoint.

server/api.go

@@ -10,8 +10,13 @@ import (
 
 	"github.com/coreos/dex/api"
 	"github.com/coreos/dex/storage"
+	"github.com/coreos/dex/version"
 )
 
+// apiVersion increases everytime a new call is added to the API. Clients should use this info
+// to determine if the server supports specific features.
+const apiVersion = 0
+
 // NewAPI returns a server which implements the gRPC API interface.
 func NewAPI(s storage.Storage) api.DexServer {
 	return dexAPI{s: s}
@@ -159,3 +164,10 @@ func (d dexAPI) DeletePassword(ctx context.Context, req *api.DeletePasswordReq)
 	return &api.DeletePasswordResp{}, nil
 
 }
+
+func (d dexAPI) GetVersion(ctx context.Context, req *api.VersionReq) (*api.VersionResp, error) {
+	return &api.VersionResp{
+		Server: version.Version,
+		Api:    apiVersion,
+	}, nil
+}