Error out on secret/config templates for older API

Makes sure if the user specifies an older API version that we don't pass
through templating options for versions that templating was not
supported.

Signed-off-by: Brian Goff <cpuguy83@gmail.com>

api/server/router/swarm/cluster_routes.go

@@ -372,6 +372,10 @@ func (sr *swarmRouter) createSecret(ctx context.Context, w http.ResponseWriter,
 	if err := json.NewDecoder(r.Body).Decode(&secret); err != nil {
 		return err
 	}
+	version := httputils.VersionFromContext(ctx)
+	if secret.Templating != nil && versions.LessThan(version, "1.36") {
+		return errdefs.InvalidParameter(errors.Errorf("secret templating is not supported on the specified API version: %s", version))
+	}
 
 	id, err := sr.backend.CreateSecret(secret)
 	if err != nil {
@@ -440,6 +444,11 @@ func (sr *swarmRouter) createConfig(ctx context.Context, w http.ResponseWriter,
 		return err
 	}
 
+	version := httputils.VersionFromContext(ctx)
+	if config.Templating != nil && versions.LessThan(version, "1.36") {
+		return errdefs.InvalidParameter(errors.Errorf("config templating is not supported on the specified API version: %s", version))
+	}
+
 	id, err := sr.backend.CreateConfig(config)
 	if err != nil {
 		return err