add build tags to disable kms providers

kms/vault.go

@@ -1,13 +1,22 @@
+// +build !novaultkms
+
 package kms
 
-const (
-	vaultProviderName = "VaultTransit"
+import (
+	// we import hashivault here to be able to disable Vault support using a build tag
+	_ "gocloud.dev/secrets/hashivault"
+
+	"github.com/drakkan/sftpgo/version"
 )
 
 type vaultSecret struct {
 	baseGCloudSecret
 }
 
+func init() {
+	version.AddFeature("+vaultkms")
+}
+
 func newVaultSecret(base baseSecret, url, masterKey string) SecretProvider {
 	return &vaultSecret{
 		baseGCloudSecret{