fix pagination

Author: giancarloromeo

services/api-server/src/simcore_service_api_server/api/routes/solvers.py

@@ -257,7 +257,7 @@ async def list_solver_ports(
         product_name=product_name,
     )
 
-    return OnePage[SolverPort](items=ports)
+    return OnePage[SolverPort].model_validate(dict(items=ports))
 
 
 @router.get(

services/api-server/src/simcore_service_api_server/models/pagination.py

@@ -18,7 +18,7 @@
     MAXIMUM_NUMBER_OF_ITEMS_PER_PAGE,
 )
 from models_library.utils.pydantic_tools_extension import FieldNotRequired
-from pydantic import BaseModel, ConfigDict, NonNegativeInt, field_validator
+from pydantic import BaseModel, ConfigDict, NonNegativeInt, ValidationInfo, field_validator
 
 T = TypeVar("T")
 
@@ -50,12 +50,12 @@ class OnePage(BaseModel, Generic[T]):
     """
 
     items: Sequence[T]
-    total: NonNegativeInt = FieldNotRequired()
+    total: NonNegativeInt = FieldNotRequired(validate_default=True)
 
     @field_validator("total", mode="before")
     @classmethod
-    def check_total(cls, v, values):
-        items = values["items"]
+    def _check_total(cls, v, info: ValidationInfo):
+        items = info.data.get("items", [])
         if v is None:
             return len(items)