Bug/creation time filter (#270)

* filter more in the pass

* add test

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* add optional

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: peterdudfield

nowcasting_datamodel/models/forecast.py

@@ -8,7 +8,7 @@
 
 import logging
 from datetime import datetime
-from typing import List
+from typing import List, Optional
 
 import numpy as np
 from pydantic import Field, PrivateAttr, validator
@@ -306,7 +306,7 @@ class ForecastValue(EnhancedBaseModel):
         ..., ge=0, description="The forecasted value in MW"
     )
 
-    expected_power_generation_normalized: float = Field(
+    expected_power_generation_normalized: Optional[float] = Field(
         None, ge=0, description="The forecasted value divided by the gsp capacity [%]"
     )