fixed pydantic schema for MeasurementCreate

src/logic/database/Schemas.py

@@ -3,7 +3,6 @@ from enum import Enum
 from typing import List
 
 from pydantic import BaseModel, Field
-from typing import Optional
 
 
 # ===== special =====
@@ -73,7 +72,7 @@ class Measurement(BaseModel):
 
 class MeasurementCreate(BaseModel):
     value: str = Field(..., min_length=1)
-    timestamp: Optional[str]
+    timestamp: str | None = None
     sensor_id: int