core:services:helper: Allow optional metadata

* Allow ServiceInfo model to receive optional metadata field to avoid
  validation error

Author: joaomariolago

core/services/helper/main.py

@@ -112,7 +112,7 @@ class ServiceInfo(BaseModel):
     versions: List[str]
     port: int
     path: Optional[str]
-    metadata: Optional[ServiceMetadata]
+    metadata: Optional[ServiceMetadata] = None
 
     def __hash__(self) -> int:
         return hash(self.port)