Make product API versions independently installable

backend/product/app/api/config.go

@@ -7,6 +7,8 @@ import (
 )
 
 type Config struct {
+	// nil preserves the legacy v1 mount; an explicit empty list installs no API.
+	Versions      []Mount                    `yaml:"versions"`
 	Notifications *notifications.Config      `yaml:"notifications"`
 	Mw            *mwa.Config                `yaml:"middleware"`
 	AuthStorage   *mwa.AuthStorageConfig     `yaml:"auth_storage"`