feat: service token introduction

db/models/__init__.py

@@ -2,6 +2,7 @@ from .addons import Addon
 from .invoice import Invoice
 from .orders import Order, OrderAddon
 from .pricing import PricingConfig
+from .service_signatures import ServiceSignature
 from .sessions import Session
 from .subscription_addons import SubscriptionAddon
 from .subscriptions import Subscription
@@ -15,6 +16,7 @@ __all__ = [
     "Order",
     "OrderAddon",
     "PricingConfig",
+    "ServiceSignature",
     "Session",
     "Subscription",
     "SubscriptionAddon",