fix typecheck

Author: giancarloromeo

services/director-v2/src/simcore_service_director_v2/models/dynamic_services_scheduler.py

@@ -35,6 +35,7 @@
 from pydantic import (
     AnyHttpUrl,
     BaseModel,
+    BeforeValidator,
     ConfigDict,
     Field,
     StringConstraints,
@@ -476,7 +477,8 @@ def get_proxy_endpoint(self) -> AnyHttpUrl:
     ] = None
 
     product_api_base_url: Annotated[
-        AnyHttpUrl | None,
+        str | None,
+        BeforeValidator(lambda v: f"{AnyHttpUrl(v)}"),
         Field(
             description="Base URL for the current product's API.",
         ),